Biology

 

The Nature and Variety of Living Organisms 1.1 Characteristics of living organisms Movement Movement is an action by an organism or part of an organism causing a change of position or place. For example, climbing plants move their tendrils (growths from their stems) around fixed objects so that they can climb walls Respiration Respiration is the chemical reactions in cells that break down nutrient molecules and release energy for metabolism (chemical reactions in cells). For example, when a human eats an apple, the sugars in the apple are broken down to release energy. Sensitivity Sensitivity is the ability to detect or sense stimuli in the internal or external environment and to make appropriate responses. For example, a deer detects movement in the nearby grass and runs away from a potential predator. Growth Growth is a permanent increase in size and dry mass (without including the water in the organism) by an increase in cell number or cell size or both. For example, a puppy will grow very rapidly in its first few months and will never return to its original tiny size. Reproduction Reproduction is the processes that make more of the same kind of organism. For example, bacterial cells can split in two to make two bacterial cells. Excretion Excretion is the removal from organisms of waste products from metabolism, toxic materials, and substances which are in excess of requirements. For example, oxygen is a waste product made by plants, and it leaves the plant through its leaves. Nutrition Nutrition is the taking in of materials for energy, growth and development. For example, plants take in light, water and carbon dioxide, and animals need organic compounds and water. Control Organisms are in control of their internal environments. Keeping internal conditions (such as temperature) the same is known as homeostasis. 1.2-1.4 Variety of living organisms Eukaryotic cells Eukaryotic cells are found in plants, animals, fungi and Protoctista (single-celled organisms that don’t fit other categories). They are 10-100 micrometres in size. A eukaryote is an organism made up of eukaryotic cells. Prokaryotic cells They are 0.1 - 5.0 micrometres in size. A prokaryote is an organism made up of prokaryotic cells. Bacteria are prokaryotes. Animals Animal cells have no cell wall and no chloroplasts (so do not carry out photosynthesis). Animals are multicellular (made of many cells) and they don't make their own food, but they store carbohydrates as glycogen. They often have nervous coordination (using nerves) and are able to move around. Mammals (like whales) and insects (like mosquitoes) are examples. Plants Plant cells are surrounded by cell walls (made of a substance called cellulose) and contain chloroplasts (carry out photosynthesis). Plants are multicellular (many cells) and they make their own carbohydrate food, which they store as sucrose or starch. Plants can be divided into flowering and non-flowering plants. Flowering plants include cereals (e.g. maize) and herbaceous legumes (e.g. peas). Non-flowering plants include pines and ferns. Fungi Fungi cells have cell walls (that contain a substance called chitin) and no chloroplasts. Fungi can be multicellular or unicellular and they are saprotrophic (they feed by secreting digestive enzymes and absorbing broken down decaying matter), and often store carbohydrates as glycogen. Their bodies are made up of mycelium, which contains many thread-like structures called hyphae. Mushrooms and single-celled yeast are examples. Fungal cells are similar to plant cells, apart from: There are no chloroplasts in fungal cells. The cell walls of fungal cells are made from chitin instead of cellulose. Fungi can be unicellular or multicellular and are made up of hyphae (thread-like structures). The hyphae are able to grow and penetrate tissues, such as human skin or the surface of plants. Athlete's foot is caused by fungi. Bacteria Bacteria are unicellular and they have cell walls and circular loops of...

Structures and Functions in Living Organisms 2.1 Level of organisation Organelle (e.g. cytoplasm): subcellular structures found within living cells Cell (e.g. muscle cell / palisade cell): basic structural unit of a living organism Tissue (e.g. muscle tissue / palisade tissue): group of similar cells working together to carry out a particular function Organ (e.g. stomach / leaf): group of different tissues working together to carry out a particular function Organ system (e.g. digestive system / shoot system): group of organs working together to carry out a particular function Organism (e.g. human / sunflower): a form of life 2.2-2.6 Cell Structure Nucleus: stores genetic material Cytoplasm - where chemical reactions take place Cell membrane: controls which substances can pass in and out of the cell Mitochondria: provides energy for the cell through respiration Ribosomes: site of protein synthesis Rigid cell wall (plants): provides support and structure Chloroplasts (plants): carry out photosynthesis with chlorophyll absorbing light from the sun Permanent vacuole (plants): contains cell sap (sugars, salts, water) 2.7-2.14 Biological molecules Carbohydrates: carbon, hydrogen, oxygen, starch and glycogen from simple sugars (e.g. glucose, fructose) Proteins: carbon, hydrogen, oxygen, nitrogen, proteins from amino acids Lipids: carbon, oxygen, hydrogen, lipids from 3 fatty acids + glycerol Glucose test: benedict's solution + water bath, blue to brick-red Starch test: iodine, brown to blue-black Protein test: biuret A + biuret B, blue to purple Fat test: ethanol + distilled water, colourless to milky white emulsion Enzyme: biological catalysts which increase the rate of reaction Enzymes + temperature: rate increases as temperature increases (particles have more kinetic energy so move faster and higher chances of collision), optimum 37 Enzymes + high temperature: bonds are broken, active site changes shape, enzyme cannot bind with the substrate, enzyme is denatured Enzyme + temperature exp: heat starch to set temperature, add amylase, add iodine to each well after a minute, measure time till iodine stops turning blue-black Enzyme  + temperature exp: independent - temperature, dependent - rate of starch breakdown, control - volume of starch, concentration of starch Enzymes + pH: rate increases as neutrality increases (particles have more kinetic energy so move faster and higher chances of collision), optimum 7 Enzymes + high pH: bonds are broken, active site changes shape, enzyme cannot bind with the substrate, enzyme is denatured Enzyme + pH exp: heat starch + amylase + pH solution, add a drop of the solution to each well with iodine after 10 seconds, measure time till solution turns orange Enzyme + pH exp: independent - pH, dependent - rate of starch breakdown, control - temperature, volume of starch, concentration of starch 2.15-2.17 Movement of substances into and out of cells Diffusion: the net movement of particles from an area of high concentration to an area of low concentration Diffusion example: single-celled organisms use diffusion to transport molecules into the body from the air as they have a large surface area : volume ratio Diffusion + concentration gradient: the greater the difference in concentration, the quicker the rate of diffusion (more particles are moving down the gradient) Diffusion + temperature: the greater the temperature, the quicker the rate of diffusion (particles have more kinetic energy so move faster and collide frequently) Diffusion + surface area : volume ratio: the greater the surface area, the quicker the rate of diffusion (particles have more space to move through) Diffusion + distance: the lower the distance particles need to travel, the quicker the rate of diffusion Active transport: the movement of particles from an area of low concentration to an area of high concentration using energy Active transport example: root hair cells use diffusion to take mineral ions...

Ecology and the Environment 4.1-4.5 The Organism in the Environment Population: all the organisms of one species living in the same habitat Community: all the populations of organisms that live in an area or ecosystem Habitat: a small part of an ecosystem where a species lives Ecosystem: a system in which organisms interact with each other and their environment Biodiversity: a measure of the variety of organisms in an area Population exp: random number generator for grid coordinates to place quadrat, count how many in each quadrat, find number per square metre, multiply by area Distribution exp: tape measure, place a quadrat at equal lengths along the transect, count how many in each quadrat Abiotic: light intensity - light required for photosynthesis, temperature - affects the rate of photosynthesis, water levels - needed to survive Biotic: food availability - organisms can breed successfully, pathogens - can kill organisms, competition - some animals can't get food or water 4.6-4.9 Feeding Relationships Producer: an organism that produces its own food Primary: an animal that eats plants (a herbivore) Secondary: an animal that eats primary consumers Tertiary: an animal that eats secondary consumers Decomposer: an organism that causes decay of dead material (fungi and bacteria) Food chain: shows the feeding relationships between organisms Food web: shows many interdependent food chains Pyramid of number: shows the population at each trophic level, often a pyramid shape, for a large plant the bar size is small as 1 tree feeds many insects Pyramid of biomass: shows the biomass at each trophic level, often a pyramid shape, not all the food consumed is converted into biomass Pyramid of energy: shows the energy content at each trophic level, always a pyramid shape Energy loss: 10% transferred as organisms don't normally eat every part, bits they eat might not be absorbed, biomass gets released as waste products 4.10-4.11 Cycles within Ecosystems Combustion: burning of fossil fuels which releases carbon back into the atmosphere Decomposition (Carbon cycle): dead plants and animals are broken down by decomposers and carbon returns to the atmosphere Respiration: plants and animals respire which releases carbon dioxide into the atmosphere Photosynthesis: plants remove carbon dioxide from the atmosphere through photosynthesis Fossil fuels: fuels formed organic material, such as peat, coal, oil, and natural gas Nitrogen fixing: nitrogen fixing bacteria convert nitrogen in the atmosphere into nitrates in the soil Nitrification: nitrifying bacteria convert ammonia into nitrates in the soil Decomposition (Nitrogen cycle): decomposers convert decaying matter into ammonia Denitrification: denitrifying bacteria convert nitrates in the soil into nitrogen in the atmosphere 4.12-4.8 Human Influences on the Environment Sulphur dioxide: releases when fossil fuels are burnt, dissolves in water, falls as acid rain, low pH in lakes so fish die, corrodes limestone in buildings Carbon monoxide: released when fossil fuels are burnt through incomplete combustion, binds with haemoglobin, no O2 can bind, less O2 transported, people die Methane (greenhouse gas): comes from cattle farming and causes global warming Water vapour (greenhouse gas): comes from combustion and causes global warming CFC (greenhouse gas): comes from refrigerators and affects the ozone layer Carbon dioxide (greenhouse gas): comes from burning fossil fuels and causes global warming Nitrous oxide (greenhouse gas): comes from burning fossil fuels and causes acid rain Greenhouse effect: greenhouse gases absorb sun's heat, trap it above the Earth's surface, which leads to higher temperatures and global warming Global warming effects: glaciers melt, water levels rise, loss of habitats, changes om weather patterns Eutrophication: nutrients allow rapid growth of algae, algal bloom stops light reaching aquatic plants, oxygen depletion means other aquatic organisms...

Use of Biological Resources 5.1-5.9 Food Production: Maintaining water quality: filter water to remove waste and harmful bacteria to prevent disease Controlling intraspecific predation: stops competition within the same species, as fish are separated by size and age to prevent competition Controlling interspecific predation: stops competition between species, as different species are separated by nets or tanks Controlling disease: antibiotics are given to increase chances of survival Removal of waste products: water is filtered to remove waste faeces Controlling feeding quality + frequency: fish are fed frequently in small amounts so they don't overeat and to avoid food wastage Selective breeding: reproduce fish with desired characteristics