Biology (B2)

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Description

A mindmap for Biology Unit 2 (B2) for AQA.

Resource summary

Biology (B2)
  1. B2.1 - Cells, tissues and organs
    1. Animal and plant cells
      1. Human cells

        Annotations:

        • Use this acronym to remember what is in a human cell: Nice Chicken Curry Mild Rice
        1. Nucleus

          Annotations:

          • Controls the cell's activities
          1. Cytoplasm

            Annotations:

            • Many chemical reactions take place.
            1. Cell membrane

              Annotations:

              • Controls the movement of materials in and out of cell.
              1. Mitochondria

                Annotations:

                • Energy is released during aerobic respiration
                1. Ribosomes

                  Annotations:

                  • Protein synthesis takes place
                2. Plant cells

                  Annotations:

                  • Contain all the things in a human cell, with these extra:
                  1. Cell wall

                    Annotations:

                    • Made of cellulose for support
                    1. Chloroplasts

                      Annotations:

                      • Contain chlorophyll for photosynthesis. The light energy is absorbed to make food.
                      1. Permanent vacuole

                        Annotations:

                        • Contains cell sap
                    2. Bacteria and yeast

                      Annotations:

                      • -Very small and can only be seen by a microscope.
                      1. Bacteria

                        Annotations:

                        • Contains a cell membrane and cytoplasm surrounded by a cell wall.
                        • NO NUCLEUS - genetic material is in the cytoplasm
                        • Multiplied bacteria = bacterial colony
                        1. Yeast

                          Annotations:

                          • -SINGLE-CELLED organism -Have a nucleus, cytoplasm and a membrane surrounded by a cell wall.
                        2. Specialized cells

                          Annotations:

                          • -Cells are specialized to carry out a specific function. -The structure of the cell gives clues as to what it does.
                          1. Muscle cells

                            Annotations:

                            • Many mitochondria to create a lot of energy.
                            1. Gland cells

                              Annotations:

                              • Many ribosomes to create a lot of protein.
                              1. Neurons

                                Annotations:

                                • Specialized to carry impulses from receptors to the CNS.
                              2. Diffusion

                                Annotations:

                                • The spreading out of the particles of a gas, or of any substance in a solution.
                                1. Concentration

                                  Annotations:

                                  • NET MOVEMENT into or out of cells depends on concentration on either side of cell membrane.
                                  • Difference in concentration between two areas is: CONCENTRATION GRADIENT
                                  1. Increasing diffusion

                                    Annotations:

                                    • Rate is increased when: -Distance is decreased. -Surface area is increased. -Concentration gradient is increased.
                                    1. Examples

                                      Annotations:

                                      • Diffusion of oxygen into cells of body from the bloodstream. Due to respiration of cells.
                                      • Diffusion of carbon dioxide into actively photosynthesizing plant cells.
                                      • Diffusion of simple sugars and amino acids from gut through cell membranes.
                                    2. Tissues and organs
                                      1. Tissues

                                        Annotations:

                                        • A tissue is a group of cells with similar structure and function.
                                        1. Animal tissues

                                          Annotations:

                                          • Muscle tissue - Can contract to bring about movement.
                                          • Glandular tissue - To produce substances such as enzymes or hormones.
                                          • Epithelial tissue - Covers some parts of the body.
                                          1. Plant tissues

                                            Annotations:

                                            • Epidermal tissue - Covers the plant
                                            • Mesophyll - Can photosynthesize
                                            • Xylem and phloem - transport substances around the plant.
                                          2. Organs

                                            Annotations:

                                            • Organs are made of several tissue types.
                                            1. The stomach

                                              Annotations:

                                              • The stomach is an organ made up of: -Muscular tissue to churn the stomach contents. -Glandular tissue to produce DIGESTIVE JUICES. -Epithelial tissue to cover the outside and the inside of the stomach.
                                          3. Organ systems

                                            Annotations:

                                            • Groups of organs work together in an organ system.
                                            1. The digestive system

                                              Annotations:

                                              • The digestive system in humans is adapted to exchange substances with the environment.
                                              • It includes: -Glands, such as the pancreas and salivary glands which produce digestive juices. -Stomach and small intestine where digestion occurs. -Liver which produces bile. -Small intestine where the absorption of soluble food occurs. -The large intestine where water is absorbed from undigested food, producing faeces. 
                                          4. B2.2 - Organisms in the environment
                                            1. Photosynthesis

                                              Annotations:

                                              • During photosynthesis, light energy is transferred to chemical energy.
                                              • Some of the glucose is converted into insoluble starch for storage.
                                              1. Equation

                                                Annotations:

                                                • Carbon Dioxide + Water → Glucose + Oxygen
                                                • 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂   
                                                1. Process

                                                  Annotations:

                                                  • 1. CO₂ taken in by leaves, water taken in by roots. 2. Chlorophyll traps light energy. 3. Energy is used to convert the CO₂ and H₂0 to C₆H₁₂O₆
                                                  1. Testing

                                                    Annotations:

                                                    • -Testing leaves with iodine solution, to test for starch.  -Green patches will turn solution blue-black to show starch has been made.
                                                    1. Variegated leaves

                                                      Annotations:

                                                      • Different patches = difference in chlorophyll. Green = Chlorophyll White = No Chlorophyll
                                                  2. Limiting factors

                                                    Annotations:

                                                    • 3 limiting factors: -Lack of light -Cold (enzymes slower) -Little carbon dioxide
                                                    1. Experiments

                                                      Annotations:

                                                      • Independent variable: Concentration of Carbon Dioxide
                                                      • Dependent Variable: Volume of Oxygen produced.
                                                      • Control variables: Light, temperature, type of plant
                                                    2. How plants use glucose

                                                      Annotations:

                                                      • -Converted into insoluble starch for storage. -Respiration -Converted into lipids  and oils for storage. -Produce cellulose which strengthens cell walls. -Produce proteins.
                                                      1. Ions

                                                        Annotations:

                                                        • Plant and algal cells need a supply of mineral ions such as: -Nitrate ions to produce protein. --Plants absorb nitrate ions from soil. --Algae absorb nitrate ions from the water in which they live.
                                                      2. Making the most out of photosynthesis

                                                        Annotations:

                                                        • Plant growers can artificially control the environment to improve plant growth.
                                                        • To improve plant growth, the factors that need to be controlled are: -Light intensity -Temperature -Carbon dioxide levels
                                                        1. Organisms in their environment

                                                          Annotations:

                                                          • The distribution of organisms is affected by environmental factors.
                                                          • -Temperature -Availability of nutrients -Amount of light -Availability of water -Availability of oxygen -Availability of carbon dioxide
                                                          1. Measuring the distribution of organisms

                                                            Annotations:

                                                            • Quantitative data is used to describe how physical factors might be affecting the distribution of organisms in a habitat.
                                                            • There are two ways to obtain quantitative data: -Random quantitative sampling using a quadrat. -Sampling along a transect.
                                                            1. Quadrat

                                                              Annotations:

                                                              • -A square from which may be subdivided into a grid.  -Several quadrats are placed randomly and the thing being investigated is counted in each one. -It can be used to estimate the number of species or plant in a field.
                                                              1. Transect

                                                                Annotations:

                                                                • -This is not random. A line is marked between two points, and a random quadrat placed every 5 metres along the line. -Supplies a lot of information about:  --Habitat --Organisms in it.
                                                                1. Sample size

                                                                  Annotations:

                                                                  • In a large field, enough random quadrats are needed so that the sample is representative of the entire field.
                                                              2. B2.3 - Enzymes
                                                                1. Proteins, catalysts and enzymes
                                                                  1. Proteins

                                                                    Annotations:

                                                                    • -Made up of long chains of amino acids. -Long chains are folded to produce specific shapes, which have a specific function.
                                                                    • They can be: -Structural components of tissues -Hormones -Antibodies -Catalysts
                                                                    1. Enzymes

                                                                      Annotations:

                                                                      • -Biological catalysts -Large proteins and the shape is vital for its function. -The 'active site' is the area where other molecules can fit.
                                                                      • In a reaction, the substrate can: -Be held in the active site. -Be connected to another molecule. -Be broken down.
                                                                      • Enzymes can: -Build large molecules from smaller ones. --Starch from glucose molecules -Change one molecule into another -Break down large molecules into small ones.
                                                                    2. Factors affecting enzyme action

                                                                      Annotations:

                                                                      • -Reactions take place quicker if it is warmer. --At higher temperatures the molecules move around more quickly and so collide with each other more often, with more energy. (Learn this word for word)
                                                                      • -Each enzyme works best at a particular pH value.
                                                                      1. Denaturing

                                                                        Annotations:

                                                                        • If the temperature gets too hot, the active site CHANGE SHAPE, causing the enzyme to stop working.
                                                                        • If the pH is too acidic or too alkaline for the enzyme, the active site could change shape.
                                                                      2. Digestion

                                                                        Annotations:

                                                                        • -These enzymes are produced in the glands and in the lining of the gut. -Enzymes pass out of the cells and come into contact with food. -Digestion involves the breakdown of large, insoluble molecules into smaller soluble ones.
                                                                        1. Special enzymes
                                                                          1. Amylase

                                                                            Annotations:

                                                                            • Produced in the salivary glands, the pancreas and the small intestine.
                                                                            • Catalyses the digestion of starch into sugar in mouth and small intestine.
                                                                            • Work best when the conditions are slightly alkaline.
                                                                            1. Protease

                                                                              Annotations:

                                                                              • Produced by the stomach, pancreas and small intestine.
                                                                              • Catalyses the breakdown of proteins into amino acids in the stomach and small intestine.
                                                                              • Work best when the conditions are acidic.
                                                                              1. Lipase

                                                                                Annotations:

                                                                                • Produced by the pancreas and small intestine.
                                                                                • Catalyses the breakdown of lipids to fatty acids and glycerol.
                                                                                • Work best when the conditions are slightly alkaline.
                                                                              2. Bile

                                                                                Annotations:

                                                                                • -The liver produces bile. -Stored in the gall bladder before being released into the small intestine. -Bile neutralises the acid that was added to food in the stomach. -This provides alkaline conditions in which enzymes in the small intestine work most effectively.
                                                                              3. Uses
                                                                                1. Biological detergents

                                                                                  Annotations:

                                                                                  • -Contain proteases and lipases that digest food stains. -Work at lower temperatures than ordinary washing powders. -Saves energy and money spent on electricity.
                                                                                  1. Baby foods

                                                                                    Annotations:

                                                                                    • Proteases are used to pre-digest proteins in some baby foods.
                                                                                    1. Fructose syrup

                                                                                      Annotations:

                                                                                      • -Isomerase is used to convert glucose syrup into fructose syrup.  -Fructose is MUCH SWEETER so less is needed in foods. -Foods are less fattening. 
                                                                                      1. Foods

                                                                                        Annotations:

                                                                                        • Carbohydrases are used to convert starch into sugar syrup for use in foods.
                                                                                        1. Industry

                                                                                          Annotations:

                                                                                          • -Used to bring about reactions at normal temperatures and pressures. -Traditional chemical processes require: --Expensive equipment. --A lot of energy (to produce high temperatures and pressures)
                                                                                        2. High-tech enzymes
                                                                                          1. Advantages

                                                                                            Annotations:

                                                                                            • -Enzymes in biological washing powders are very effective at removing stains. -Biological washing powders can be used at lower temperatures. -Used in medicine to diagnose, control or cure disease. -Industry, costs of equipment and energy can be reduced.
                                                                                            1. Disadvantages

                                                                                              Annotations:

                                                                                              • -Misuse of washing powders can cause allergic reactions on skin. -Enzymes may enter waterways via the sewage system. -Industrial enzymes are costly. -Enzymes denature at high temperatures needed to kill pathogens in the washing. -Fabrics such a wool are digested by proteases.
                                                                                          2. B2.4 - Energy from respiration
                                                                                            1. Aerobic respiration

                                                                                              Annotations:

                                                                                              • -Takes place continually. -Chemical reactions take place in the mitochondria and are controlled by enzymes.
                                                                                              1. Equation

                                                                                                Annotations:

                                                                                                • Glucose + oxygen  → Carbon dioxide + water [+ energy]
                                                                                                1. Uses

                                                                                                  Annotations:

                                                                                                  • Energy released used to: -Build larger molecules. -Enable muscle contraction. -Maintain a constant body temperature in colder surroundings. -Build sugars, nitrates and other nutrients into amino acids and then proteins in plants.
                                                                                                  1. Experiment

                                                                                                    Annotations:

                                                                                                    • -Measure volume of carbon dioxide produced.
                                                                                                  2. Effect of exercise on the body

                                                                                                    Annotations:

                                                                                                    • -During exercise muscles need more energy. -More glucose and oxygen need to be transported to the muscles.
                                                                                                    1. Heart rate

                                                                                                      Annotations:

                                                                                                      • Increase and the blood vessels dilate to allow more blood containing oxygen and glucose to reach the muscles.
                                                                                                      1. Breathing

                                                                                                        Annotations:

                                                                                                        • Increase in breathing rate and depth of each breath to allow a greater uptake of oxygen and release of carbon dioxide in the lungs.
                                                                                                        1. Glycogen

                                                                                                          Annotations:

                                                                                                          • Muscles store glucose at glycogen which can be converted back to glucose during exercise.
                                                                                                        2. Anaerobic respiration

                                                                                                          Annotations:

                                                                                                          • When muscles work hard for a long time, they may have too little oxygen and become fatigued.
                                                                                                          • Muscles use anaerobic respiration if they are short of oxygen.
                                                                                                          • Anaerobic respiration doesn't break down glucose fully, therefore less energy is released from the glucose.
                                                                                                          1. Equation

                                                                                                            Annotations:

                                                                                                            • glucose → lactic acid (+ energy released)
                                                                                                            1. Oxygen debt

                                                                                                              Annotations:

                                                                                                              • In anaerobic respiration, lactic acid replaces carbon dioxide and water as the waste product.
                                                                                                              • When the exercise is complete, the lactic acid MUST be broken down.
                                                                                                              • The extra oxygen you need to oxidize the lactic acid into carbon dioxide and water is called oxygen debt.
                                                                                                          2. B2.5 - Simple inheritance in animals and plants
                                                                                                            1. Cell division

                                                                                                              Annotations:

                                                                                                              • Necessary for the growth of an organism, or for the repair of damaged tissues.
                                                                                                              1. Mitosis

                                                                                                                Annotations:

                                                                                                                • Two identical cells being produced from the original cell. Mitosis = Making Identical Two
                                                                                                                • Two identical cells being produced from the original cell. 46 chromosomes (2 sets) Mitosis = Making Identical Two
                                                                                                                1. Chromosomes

                                                                                                                  Annotations:

                                                                                                                  • Found in pairs and contain genes (alleles) which must be passed onto each new cell.
                                                                                                                  1. Process

                                                                                                                    Annotations:

                                                                                                                    • -Normal body cell has 46 chromosomes (23 pairs). -Copies of these pairs are made. -Then the cell divides once to form two genetically identical body cells.
                                                                                                                  2. Meiosis

                                                                                                                    Annotations:

                                                                                                                    • -Cells in reproductive organs divide by meiosis to form gametes.  -23 chromosomes (one set) -Meiosis = Making Eggs
                                                                                                                    1. Process

                                                                                                                      Annotations:

                                                                                                                      • -Before division, a copy of each chromosome is made. -The cell now divides twice to form four gametes. -Each gamete has a single set of chromosomes with a different combination of genes. 
                                                                                                                      1. Sexual reproduction

                                                                                                                        Annotations:

                                                                                                                        • -Results in variation as the gametes from each parent fuse. -Half genetic information from mother, half from father. -In fertilization, a single body cell with new pairs of chromosomes form. -Individual develops through mitosis. 
                                                                                                                      2. Differentiation

                                                                                                                        Annotations:

                                                                                                                        • Most animal cells differentiate early in development and cell division is mainly for: -Repair -Replacement
                                                                                                                        • Plant cells can differentiate throughout the life of the plant as it continues to grow.
                                                                                                                        1. Asexual

                                                                                                                          Annotations:

                                                                                                                          • Asexual reproduction cells are produced by mitosis from the parent cell. They contain the SAME alleles as the parents.
                                                                                                                        2. Stem cells

                                                                                                                          Annotations:

                                                                                                                          • -Unspecialised. -Found in human embryo and bone marrow. -Differentiate into different types of body cell. -Adult bone marrow stem cells - can differentiate into blood cells.-Hoped that stem cells could be used to cure diseases.
                                                                                                                          1. Embryos

                                                                                                                            Annotations:

                                                                                                                            • Embryonic stem cells can be used in medical research and treatments.
                                                                                                                            • Found: -Spare embryos from IVF. -Created from adult cells. -Taken from the umbilical cord of newborn babies.
                                                                                                                            1. Issues
                                                                                                                              1. Economical

                                                                                                                                Annotations:

                                                                                                                                • Very expensive to carry out research using embryonic cells.
                                                                                                                                1. Ethical

                                                                                                                                  Annotations:

                                                                                                                                  • -The research is experimental. -Embryos have potential to become a baby and are destroyed. -Embryo cannot give permission.
                                                                                                                                2. Embryo screening

                                                                                                                                  Annotations:

                                                                                                                                  • Involves tests to diagnose disorders before the baby is born.
                                                                                                                                  1. Results

                                                                                                                                    Annotations:

                                                                                                                                    • -Sometimes parents decide to terminate the pregnancy. -Others decide it isn't ethical and keep the baby.
                                                                                                                                    • In IVF, only healthy embryos are implanted into the mother. Embryos carring FAULTY genes are destroyed, which isn't ethical.
                                                                                                                              2. Mendel to DNA

                                                                                                                                Annotations:

                                                                                                                                • A monk who worked out how characteristics were inherited.
                                                                                                                                1. Genes

                                                                                                                                  Annotations:

                                                                                                                                  • -Found on chromosomes. -Control our characteristics. -Short section of DNA.
                                                                                                                                  1. Genetic code

                                                                                                                                    Annotations:

                                                                                                                                    • Each genes codes for a particular combination of amino acids which make a specific protein.
                                                                                                                                  2. DNA

                                                                                                                                    Annotations:

                                                                                                                                    • -A very long molecule with a double helix structure (chromosomes). -Every individual (bar identical twins) has different DNA.
                                                                                                                                    1. DNA Fingerprint

                                                                                                                                      Annotations:

                                                                                                                                      • Unique DNA pattern which can be used to identify people.
                                                                                                                                  3. Inheritance
                                                                                                                                    1. Sex chromosomes
                                                                                                                                      1. Male

                                                                                                                                        Annotations:

                                                                                                                                        • An X and a Y chromosome (XY)
                                                                                                                                        1. Female

                                                                                                                                          Annotations:

                                                                                                                                          • Two X chromosomes (XX)
                                                                                                                                        2. Alleles

                                                                                                                                          Annotations:

                                                                                                                                          • Genes controlling the same characteristic.
                                                                                                                                          1. Dominent

                                                                                                                                            Annotations:

                                                                                                                                            • 'Masks' the effect of another allele.
                                                                                                                                            1. Recessive

                                                                                                                                              Annotations:

                                                                                                                                              • The dominant allele 'masks' this allele, so it has no effect.
                                                                                                                                            2. Genetic diagrams

                                                                                                                                              Annotations:

                                                                                                                                              • Biological models which can be constructed to predict and explain the inheritance of particular characteristics.
                                                                                                                                              1. Terminology
                                                                                                                                                1. Phenotype

                                                                                                                                                  Annotations:

                                                                                                                                                  • Physical appearance of the characteristic (dimples or no dimples)
                                                                                                                                                  1. Genotype

                                                                                                                                                    Annotations:

                                                                                                                                                    • The genetic make-up, which alleles does the individual inherit.  (DD, Dd, dd)
                                                                                                                                                    1. Homozygous

                                                                                                                                                      Annotations:

                                                                                                                                                      • Both alleles are the same DD (homozygous dominant) or dd (homozygous recessive).
                                                                                                                                                      1. Heterozygous

                                                                                                                                                        Annotations:

                                                                                                                                                        • The two alleles are different, Dd.
                                                                                                                                                    2. Genetic disorders

                                                                                                                                                      Annotations:

                                                                                                                                                      • If an allele is recessive, the person must inherit two recessive alleles to have the disorder.
                                                                                                                                                      • If the allele is dominant, the person has to inherit only one dominant allele to have the disorder.
                                                                                                                                                      1. Polydactyly

                                                                                                                                                        Annotations:

                                                                                                                                                        • -Caused by a dominant allele. -Where a baby is born with extra fingers or toes.
                                                                                                                                                        1. Cystic fibrosis

                                                                                                                                                          Annotations:

                                                                                                                                                          • -Caused by a recessive allele. -Affects cell membranes and causes the production of thick sticky mucus. 
                                                                                                                                                          1. Carriers

                                                                                                                                                            Annotations:

                                                                                                                                                            • People who carry a recessive allele.
                                                                                                                                                          2. Punnet squares

                                                                                                                                                            Annotations:

                                                                                                                                                            • Used to predict the chances of inheriting a disorder.
                                                                                                                                                        2. B2.6 - Old and new species
                                                                                                                                                          1. The origins of life on Earth

                                                                                                                                                            Annotations:

                                                                                                                                                            • -Believed that the Earth is 4500 million years old and that life began about 3500 million years ago. -There is DEBATE as to whether first live developed due to conditions on Earth, or whether simple life forms arrived from another planet.
                                                                                                                                                            1. Fossils

                                                                                                                                                              Annotations:

                                                                                                                                                              • -Fossils are remains of organisms from many years ago which are found in rocks. -We can learn from fossils how different organisms have changed as life developed on Earth.
                                                                                                                                                              • -The fossil record is INCOMPLETE.
                                                                                                                                                              1. How they are formed

                                                                                                                                                                Annotations:

                                                                                                                                                                • -From hard parts of animals that do not decay easily (teeth, claws) -From parts of organisms that have not decayed because some of the conditions for decay are absent (ice preservation). -When parts of the organism are replaced by other materials, such as minerals, as they decay. -As preserved traces of organisms (footprints, burrows).
                                                                                                                                                                1. Destruction

                                                                                                                                                                  Annotations:

                                                                                                                                                                  • Traces which were left are likely to have been destroyed by geological activity such as earthquakes.
                                                                                                                                                                  1. Soft-bodied

                                                                                                                                                                    Annotations:

                                                                                                                                                                    • Soft-bodied organisms didn't leave fossils.
                                                                                                                                                                2. Exploring fossil evidence

                                                                                                                                                                  Annotations:

                                                                                                                                                                  • -The fossil record is incomplete. -We can learn a lot from fossils which exist. -Some organisms have changed a lot over time. -Other have changed very little. -Some have become extinct.
                                                                                                                                                                  1. Extinction

                                                                                                                                                                    Annotations:

                                                                                                                                                                    • A species which once existed has completely died out. 
                                                                                                                                                                    1. Factors

                                                                                                                                                                      Annotations:

                                                                                                                                                                      • -A new disease may kill all members of a species. -Change in environment. -New diseases may be introduced. -A new predator may evolve or be introduced to an area that kills and eats all of a species. -A new competitor - original species may be left with little or nothing to eat. -A single catastrophic event may occur which destroys the habitat. -Natural changes in species occur over time.
                                                                                                                                                                  2. More about extinction

                                                                                                                                                                    Annotations:

                                                                                                                                                                    • The biggest influences on a species survival are changes in the environment.
                                                                                                                                                                    1. Climate change

                                                                                                                                                                      Annotations:

                                                                                                                                                                      • -A species which is very well adapted to a hot climate may become extinct in an Ice Age. -There could be insufficient food or it is too cold to breed.
                                                                                                                                                                      • -Climate change may: --Make it too cold or hot. --Make it too wet or dry. --Reduce a species food supply.
                                                                                                                                                                      1. Fossil evidence

                                                                                                                                                                        Annotations:

                                                                                                                                                                        • -Shows that there have been mass extinctions on a global scale. -Many of the species died out over a period of several million years - a short time.
                                                                                                                                                                        • -The habitat the species live in may be destroyed by catastrophic events such as a major volcanic eruption. -The environment can change dramatically following a collision between a giant asteroid and Earth.
                                                                                                                                                                        1. The dinosaurs

                                                                                                                                                                          Annotations:

                                                                                                                                                                          • No one knows why they have become extinct. Some ideas are: -The collision of a giant asteroid caused huge fires, earthquakes, landslides and tsunamis. The dust which rose blocked out the sun, lowering temperatures and causing darkness. Plants could not grow. -The extinction was a slower process due to sea ice melting and cooling the sea temperature by 9 degrees, therefore there was less plankton - less food available. 
                                                                                                                                                                        2. Isolation and the evolution of new species

                                                                                                                                                                          Annotations:

                                                                                                                                                                          • New species can arise form existing species if a group becomes isolated from the rest.
                                                                                                                                                                          1. Geographical isolation

                                                                                                                                                                            Annotations:

                                                                                                                                                                            • -Could occur if an island separates from the mainland or if a new river separates two areas. -Mountain ranges and old craters can isolate organisms. 
                                                                                                                                                                            1. Speciation

                                                                                                                                                                              Annotations:

                                                                                                                                                                              • Logical process: Isolation → Genetic variation → alleles selected → interbreeding no longer possible → new species (speciation).
                                                                                                                                                                              1. Isolation

                                                                                                                                                                                Annotations:

                                                                                                                                                                                • New species can occur following separation of two populations, as in geographical isolation. 
                                                                                                                                                                                1. Genetic variation

                                                                                                                                                                                  Annotations:

                                                                                                                                                                                  • Each population has a wide range of alleles that control their characteristics.
                                                                                                                                                                                  1. Natural selection

                                                                                                                                                                                    Annotations:

                                                                                                                                                                                    • -Occurs in both populations. -The alleles that control the characteristics which help the organism to survive are selected. -The organisms with these alleles will survive and breed.
                                                                                                                                                                                    1. Evolution

                                                                                                                                                                                      Annotations:

                                                                                                                                                                                      • If the environment, competitors, food supply and predators are different for each population, they will evolve differently. 
                                                                                                                                                                                      1. Interbreeding

                                                                                                                                                                                        Annotations:

                                                                                                                                                                                        • SPECIATION has occurred when the two populations can no longer successfully interbreed.
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