Biology (B2)

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

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1 B2.1 - Cells, tissues and organs
1.1 Animal and plant cells
1.1.1 Human cells

Annotations:

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

Annotations:

  • Controls the cell's activities
1.1.1.2 Cytoplasm

Annotations:

  • Many chemical reactions take place.
1.1.1.3 Cell membrane

Annotations:

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

Annotations:

  • Energy is released during aerobic respiration
1.1.1.5 Ribosomes

Annotations:

  • Protein synthesis takes place
1.1.2 Plant cells

Annotations:

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

Annotations:

  • Made of cellulose for support
1.1.2.2 Chloroplasts

Annotations:

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

Annotations:

  • Contains cell sap
1.2 Bacteria and yeast

Annotations:

  • -Very small and can only be seen by a microscope.
1.2.1 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
1.2.2 Yeast

Annotations:

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

Annotations:

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

Annotations:

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

Annotations:

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

Annotations:

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

Annotations:

  • The spreading out of the particles of a gas, or of any substance in a solution.
1.4.1 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
1.4.2 Increasing diffusion

Annotations:

  • Rate is increased when: -Distance is decreased. -Surface area is increased. -Concentration gradient is increased.
1.4.3 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.
1.5 Tissues and organs
1.5.1 Tissues

Annotations:

  • A tissue is a group of cells with similar structure and function.
1.5.1.1 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.
1.5.1.2 Plant tissues

Annotations:

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

Annotations:

  • Organs are made of several tissue types.
1.5.2.1 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.
1.6 Organ systems

Annotations:

  • Groups of organs work together in an organ system.
1.6.1 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. 
2 B2.2 - Organisms in the environment
2.1 Photosynthesis

Annotations:

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

Annotations:

  • Carbon Dioxide + Water → Glucose + Oxygen
  • 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂   
2.1.2 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
2.1.3 Testing

Annotations:

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

Annotations:

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

Annotations:

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

Annotations:

  • Independent variable: Concentration of Carbon Dioxide
  • Dependent Variable: Volume of Oxygen produced.
  • Control variables: Light, temperature, type of plant
2.3 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.
2.3.1 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.
2.4 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
2.5 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
2.6 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.
2.6.1 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.
2.6.2 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.
2.6.3 Sample size

Annotations:

  • In a large field, enough random quadrats are needed so that the sample is representative of the entire field.
3 B2.3 - Enzymes
3.1 Proteins, catalysts and enzymes
3.1.1 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
3.1.2 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.
3.2 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.
3.2.1 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.
3.3 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.
3.3.1 Special enzymes
3.3.1.1 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.
3.3.1.2 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.
3.3.1.3 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.
3.3.2 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.
3.4 Uses
3.4.1 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.
3.4.2 Baby foods

Annotations:

  • Proteases are used to pre-digest proteins in some baby foods.
3.4.3 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. 
3.4.4 Foods

Annotations:

  • Carbohydrases are used to convert starch into sugar syrup for use in foods.
3.4.5 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)
3.5 High-tech enzymes
3.5.1 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.
3.5.2 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.
4 B2.4 - Energy from respiration
4.1 Aerobic respiration

Annotations:

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

Annotations:

  • Glucose + oxygen  → Carbon dioxide + water [+ energy]
4.1.2 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.
4.1.3 Experiment

Annotations:

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

Annotations:

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

Annotations:

  • Increase and the blood vessels dilate to allow more blood containing oxygen and glucose to reach the muscles.
4.2.2 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.
4.2.3 Glycogen

Annotations:

  • Muscles store glucose at glycogen which can be converted back to glucose during exercise.
4.3 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.
4.3.1 Equation

Annotations:

  • glucose → lactic acid (+ energy released)
4.3.2 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.
5 B2.5 - Simple inheritance in animals and plants
5.1 Cell division

Annotations:

  • Necessary for the growth of an organism, or for the repair of damaged tissues.
5.1.1 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
5.1.1.1 Chromosomes

Annotations:

  • Found in pairs and contain genes (alleles) which must be passed onto each new cell.
5.1.1.2 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.
5.1.2 Meiosis

Annotations:

  • -Cells in reproductive organs divide by meiosis to form gametes.  -23 chromosomes (one set) -Meiosis = Making Eggs
5.1.2.1 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. 
5.1.2.2 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. 
5.1.3 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.
5.1.4 Asexual

Annotations:

  • Asexual reproduction cells are produced by mitosis from the parent cell. They contain the SAME alleles as the parents.
5.2 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.
5.2.1 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.
5.2.1.1 Issues
5.2.1.1.1 Economical

Annotations:

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

Annotations:

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

Annotations:

  • Involves tests to diagnose disorders before the baby is born.
5.2.1.2.1 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.
5.3 Mendel to DNA

Annotations:

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

Annotations:

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

Annotations:

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

Annotations:

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

Annotations:

  • Unique DNA pattern which can be used to identify people.
5.4 Inheritance
5.4.1 Sex chromosomes
5.4.1.1 Male

Annotations:

  • An X and a Y chromosome (XY)
5.4.1.2 Female

Annotations:

  • Two X chromosomes (XX)
5.4.2 Alleles

Annotations:

  • Genes controlling the same characteristic.
5.4.2.1 Dominent

Annotations:

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

Annotations:

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

Annotations:

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

Annotations:

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

Annotations:

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

Annotations:

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

Annotations:

  • The two alleles are different, Dd.
5.4.4 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.
5.4.4.1 Polydactyly

Annotations:

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

Annotations:

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

Annotations:

  • People who carry a recessive allele.
5.4.5 Punnet squares

Annotations:

  • Used to predict the chances of inheriting a disorder.
6 B2.6 - Old and new species
6.1 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.
6.1.1 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.
6.1.1.1 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).
6.1.1.2 Destruction

Annotations:

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

Annotations:

  • Soft-bodied organisms didn't leave fossils.
6.2 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.
6.2.1 Extinction

Annotations:

  • A species which once existed has completely died out. 
6.2.1.1 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.
6.3 More about extinction

Annotations:

  • The biggest influences on a species survival are changes in the environment.
6.3.1 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.
6.3.2 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.
6.3.3 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. 
6.4 Isolation and the evolution of new species

Annotations:

  • New species can arise form existing species if a group becomes isolated from the rest.
6.4.1 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. 
6.4.2 Speciation

Annotations:

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

Annotations:

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

Annotations:

  • Each population has a wide range of alleles that control their characteristics.
6.4.2.1.1.1 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.
6.4.2.1.1.1.1 Evolution

Annotations:

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

Annotations:

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