B4 - Flashcards in GCSE Biology

Explain the terms 'Community' and 'Population'

1) A community is made up of populations of different species in a habitat. 2) A population is all the organisms of one species in a habitat

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Estimate the total ant population in a 4000m^2 car park if 1m^2 area contained 80 ants

80 x 4000 = 320000 ants

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You catch 23 woodlice one day and mark their shells. The next day you catch 28 woodlice, four of which are marked. Estimate the population size

(23 x 28) / 4 = 161 woodlice

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Explain the meaning of the word 'ecosystem'. How is an ecosystem different to a habitat?

An ecosystem is all the organisms living in a particular area, as well as non-living (abiotic) conditions. Whereas a habitat is just the place where an organism lives.

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Describe how you'd carry out a transect to investigate the distribution of plant species in a field

To do a transect, you mark out a line using a tape measure and place quadrats next to eat other all the way along the line. You then count and record the organisms (in this case plants) found in the quadrats.

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What are abiotic factors?

Abiotic factors as all the non-living, physical factors in an environment- e.g. Light, temperature, water, oxygen, salinity (salt level), and soil quality.

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What is zonation?

Zonation is the gradual change in the distribution of species across a habitat

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What is biodiversity?

Biodiversity is a measure of the variety of life in an area. It includes: amount of variation between individuals of the same species in an area, number of different species in an area, and number of different habitats in an area

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Describe how biodiversity is different in a native woodland compared to a forestry plantation

Native woodlands: variety of tree species, trees are different sizes/ages, variety of plant/animal species and habitats. Forestry plantations: one species of tree, trees same age as planted at the same time, fewer plant/animal species and habitats

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Write down the balanced symbol equation for photosynthesis

6CO2 + 6H2O -> light energy / chlorophyll -> C6H12O6 + 6O2

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Explain why starch rather than glucose is used for storage in plants

Starch is insoluble which makes it good for storing because it can't dissolve in water and move away from storage areas in solution, and it doesn't affect the water concentration inside cells- soluble substances like sugar would bloat storage cells

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Describe van Helmonts experiment with a willow tree, what did it show?

He dried some soil, weighed it, and put it in a pot. He planted a willow tree weighing 2.2kg in it, and added rainwater whenever it was dry. 5 years later the tree weighed 76.7kg, the soil mass had hardly changed- tree gained mass from water.

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What were the conclusions of Priestley's experiments with mice and plans?

Plants restore something to the air that burning and breathing takes out. Today we know that substance is oxygen- a product of photosynthesis.

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Explain how experiments with isotopes have contributed to our understanding of photosynthesis

Scientists realised that plants release oxygen in photosynthesis but didn't know whether is came from CO2 or H2O. To find out, they gave plants water contained an isotope of oxygen (18), and CoO2. When it photosynthesised, it released oxygen18

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What are three limiting factors in photosynthesis

1) Light- as it increases as does photosynthesis until a certain point. 2) CO2- as it increases photosynthesis increases until a certain point. 3) Temperature- as it increases as does rate of photosynthesis, but if it's too high the enzymes denature

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Define the word diffusion

Diffusion is the net movement of particles from an area of high concentration to an area of low concentration.

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Why can't starch pass through a partially permeable membrane?

This is because starch molecules are too large.

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What is usually found covering the upper epidermis layer of a leaf?

The waxy cuticle

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Why does oxygen tend to move into leaves during the night?

This is because at this time, plants only respire due to the lack of light for photosynthesis. Lots of carbon dioxide is made in respiration, so there's a lot of it in the leaf- this means that it's mainly CO2 diffusing in and oxygen diffusing out.

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Decsribe how leaves are adapted for efficient diffusion

Leaves are broad- large surface area for gas diffusion. Thin- short distance to diffuse. Stomata on lower surface-let CO2 and O2 in/out, and allow water to escape. Guard cells surrounding stoma- control when it opens/closes for gas exchange.

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Describe how leaves are adapted to absorb light energy

Leaves are broad- large surface area exposed to light. Contains lots of chloroplasts- contain chlorophyll/other photosynthetic pigments to absorb light energy. Different pigments absorb different wavelengths- absorb more.

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Explain what osmosis is

Osmosis is the net movement of water molecules across a partially permeable memrane from a region of higher water concentration to a region of lower water concentration.

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What is tugor pressure?

When a plant is well watered, all its cells will draw water in by osmosis and become plump and swollen- turgid. The contents of the cell push against the inelastic cell wall- this is turgor pressure and helps support the plant tissues.

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How are xylem vessels adapted to their function?

They have thick side walls made of cellulose which are strong and stiff, which gives the plant support.

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What do phloem tubes transport?

Food substances (mainly sugars)

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Where are xylem and phloem found in a root?

Roots have to resist crushing as they push through the soil, so the xylem is in the centre to give it strength.

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What is the advantage to a plant having root hairs?

The cells on plant roots grow into long hairs which stick out into the soil. Each branch of a root will be convered in millions of these microscopic hairs. This give the plants a big surface area to absorb water from the soil.

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Give three ways that the transpiration stream benefits a plant

1) the constant stream of water from the ground helps keep the plant cool. 2) it provides the plant with a constant supply of water. 3) the water creates turgor pressure, helping support the plant.

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What is transpiration rate increased by?

Light intensity- brighter light opens stomata. Temperature- warmer means more energy for water particules to diffuse put of stomata. Air movement- wind sweeps water vaopur away, keeping low concentration of water in air outside leaf.

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What causes stomata to close when a plant is short of water? How does this benefit the plant?

When the guard cells are flaccid, they cause the stomata to close. Open stomata allow gases in and out for photosynthesis, they're sensitive to light so they open during the day and close at night, allowing them to conserve water.

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Name the three minerals that plants need for healthy growth

1) Nitrates 2) Phosphates 3) Potassium

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What is magnesium needed for in a plant?

It's required for making chlorophyll which is needed for photosynthesis. Plants without enough magnesium have yellow leaves.

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Give an example of a detritivore

Detritivores are an organism that feed on dead decaying material, an example is earthworms.

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Why does pickling food in vinegar help it to last longer?

Vinegar is acidic, and acid kills the decomposers.

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Give three ways that intensive farming methods reduce the energy lost at each stage in a food chain

1) using herbicides to kill weeds; more of the suns energy falling onto the fields goes to the crops. 2) using pesticides to kill insects that eat crops; no energy is transferred to another food chain. 3) Battery farming; animals waste less energy

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Give three problems associated with intensive farming

1) Destroying natural habitats of wild animals to make fields. 2) Careless use of fertilisers can polute rivers/lakes (eutrofication). 3) Pesticides disturb food chains

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Explain how pesticides can accumulate in a food chain

Pesticides sprayed onto crops to kill pests can also kill other organisms, which can cause a shortage of food/kill animals further up the food chain. Some are persistent, so they stick around in ecosystems.

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List the advantages and disadvantages of biological pest control

Advantages: no chemicals=less pollution, disruption of food chains, or health risk. Disadvantages: The predator might not eat the pest, or eat useful species instead. It's population might grow out of control or it might not stay in the area.

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Name five organic farming methods

1) using organic fertilisers 2) crop rotation 3) spraying weeds with herbicide 4) varying seed planting times 5) biological control

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Give two advantages and two disadvantages of organic farming

Advantages: fewer chemicals- less health risk, and better for the environment. Disadvantages: takes up more space. More labour intensive.

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B4

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