Biology - B3 Living together (food and ecosystems)

OCR GCSE

enzymes

Biological catalysts that have a specific active site to match a substrate

Substrate

A molecule that is changed by a reaction. Fits into specific enzyme active sites

Enzyme substrate complex

When a substrate combines with the active site of an enzyme to react

Temperature

This effects the rate of enzyme substrate complexes as it can cause particles to speed up and increase collisions

How fast a product appears

How fast substrate disappears

Photosynthesis

An endothermic reaction that creates glucose in plants and algae. Takes place in chlorophyll which contains enzymes that catalyse reactions inside of it.

testing if light is needed for photosynthesis

Place two plants in the dark for 48 hours so they use their starch stores. Move one into the light and do the starch test. Starch won’t be present in the dark plant

Limiting factors of Photosynthesis

Light → transfers energy needed for photosynthesis

Carbon Dioxide → substrate needed for photosynthesis

Temperature → Enzymes can only work at certain temperatures

Diffusion

The overall movement of particles from from an area of high concentration to an area of low concentration

Osmosis

The overall movement of water particles across a partially permeable cell membrane from an area of high concentration to an area of low concentration.

Active transport

The movement of particles across a membrane that goes against the concentration gradient using energy transferred during respiration

Exchanging substances across single celled organisms

E.g. prokaryotes → substances can diffuse straight across the cell membrane

Stomata

Little pores on the surface of a leaf that let CO2 and O2 diffuse in and out and water vapour to diffuse out. (aka transpiration). surrounded by guard cells which control the shape of the opening. They close when low on water or low on light.

Root hair cells

give plant roots greater surface area. Allows more water to diffuse in via osmosis. Allows minerals to diffuse in via Active transport.

Phloem

a column of living cells with perforated end plate which allow stuff to flow through. They have no nucleus so have a companion cell which also keeps them alive. food substances are translocated up and down the plant here.

Xylem

A column of dead cells with a lumen in the middle. Has thick walls made of cellulose and strengthened with lignin which supports the plant. Carries water and mineral ions up the stem into transpiration streams.

Transpiration

Caused by the evaporation and diffusion of water on plant surface. creates a slight shortage of water in the leaf so it draws more water from the roots which makes a stream of constant water throughout the plant.

Transpiration rate

This is effected by light intensity (brighter light, greater rate), Temperature (higher temperature, greater rate), and air movement (greater wind, greater rate)

Potometer

A potometer is a device used to measure the rate of water uptake by plants. It consists of a tube, a plant stem, and a reservoir of water. You remove one end of the capillary tube long enough for one air bubble to form which will travel along a scale as water is taken up by the plant.

Orginisation of ecosystems

Individual → a single organism

Population → all of one species in a habitat

Community → all organisms (every species) living in a habitat

Ecosystem → all organisms in a habitat including abiotic conditions

Competition factors

Plants → light, space, water, minerals from soil, seed distributors and pollinators

animals → space, shelter, food, water and mates

Abiotic

Factors that are non living such as Environmental conditions (average temperature, light intensity, moisture level and soil pH) or Toxic chemicals (bioaccumulation and eutrophication)

biotic

factors that are living such as the availability of food, number of predators or new pathogens.

Quadrat

A square frame enclosing a known area of land (e.g 1 metre^2) to compare how common organisms are in different areas.

Keys

A series of organisms to determine an unknown organism

Transect

A line across an area of land use to show how distribution of organisms change. Quadrats are used along the line to measure the amount of organisms

Producer

An organism that produces it’s own food i.e. plants

Primary consumers

Herbivores

Secondary consumers

Carnivores

Food chain

A diagram that shows what eats what in an ecosystem

Biomass

energy stored in the mass of the organisms that is eaten

trophic levels

levels in a food chain

Food webs

Diagrams that show how food chains are linked

Pyramids of mass

A pyramid displaying the biomass of every trophic level of a food chain. The producer at the bottom and the highest consumer at the top

Pyramids of number

A pyramid displaying the number of organisms on every trophic level of a food chain. The producer at the bottom and the highest consumer at the top

Loss of biomass

Energy is transferred through each organism on a food chain so not all of the biomass travels to the next trophic level.

Long chain carbohydrates

e.g starch is made of simple sugars

Proteins

made up of amino acids

Lipids

made up of fatty acids and glycerol

Benedict’s reagent

Heat reducing sugars mixed with this in a water bath and it will go from blue to brick red

Emulsion test

This is the test for lipids. Mix with ethanol and then pour into water. A milky white emulsion will for if lipids are present

Iodine

This tests for starch. Add this to the test sample and it will go blue-black if starch is present

Biuret test

This tests for proteins. Add a few drops of sodium hydroxide to make the solution alkaline then add Copper sulphate solution which will go from blue to purple if proteins are present

the Carbon cycle

• The process by which carbon moves between living organisms, the atmosphere, and the Earth.

• Carbon is absorbed by plants during photosynthesis and used to make food.

• Animals eat the plants and use the carbon to build their bodies.

• When organisms die, decomposers break down their bodies, releasing carbon back into the soil.

• Carbon can also be released into the atmosphere through respiration, combustion, and volcanic activity.

• The ocean absorbs and stores large amounts of carbon, but can also release it back into the atmosphere.

the Water cycle

• The continuous movement of water on, above, and below the surface of the Earth.

• It involves several processes, including evaporation, condensation, precipitation, and transpiration.

• Evaporation occurs when water from oceans, lakes, and rivers turns into water vapor due to heat from the sun.

• Condensation happens when water vapor in the atmosphere cools down and turns into liquid water, forming clouds.

• Precipitation occurs when water droplets in clouds become too heavy and fall to the ground as rain, snow, sleet, or hail.

• Transpiration is the process by which plants release water vapor into the atmosphere through their leaves.

• This ensures the availability of water for all living organisms on Earth. It also helps to maintain the balance of the Earth's ecosystem by regulating temperature and weather patterns.

• Human activities such as deforestation, pollution, and climate change can disrupt the water cycle and have negative impacts on the environment.

decomposers

microorganisms such as bacteria and fungi which break down deceased organisms

Rate of decomposition

This is effected by:

• Oxygen availability → though some decomposers work anaerobically they work much slower so plenty of oxygen is needed

• Temperature → decomposers contain enzymes to help break down the organisms so higher temperatures are better

• Water availability → decomposers need water to survive but too much water means no oxygen, so moist conditions are best

Decomposers and global warming

landfill sites tend to be low in oxygen so decomposers respire anaerobically which produces methane, a powerful greenhouse gas more so that carbon dioxide