GCSE Biology B4

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  • Created by: Ruqayya11
  • Created on: 16-04-17 13:31
What is an ecosystem made up of?
All the organisms living in an area, as well as the non-living conditions (temperature and soil quantity)
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Explain what is meant by the term population?
The number of a particular plant or animal present in the community
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What is a natural ecosystem?
A natural ecosystem, e.g. native woodlands and lakes, is where there is minimal human input. They have a large variety of plants and animals- good biodiversity
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What is an artificial ecosystem?
An artificial ecosystem, e.g. forestry plantations and fish farms, are systems created by humans. They have poor biodiversity
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What is the difference between an artificial and natural ecosystem?
In an artificial ecosystem, humans deliberately keep and protect only one species and remove any competition. This does not happen in a natural ecosystem
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Identify 4 methods of sampling organisms?
Quadrats, Sweeper nets, Pooters and Pitfall traps
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What is a pooter?
A pooter is a small jar used for collecting insects. It has two tubes, one for your mouth and the other to catch the insect
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What is a pitfall trap?
It consists of a container buried in the ground. There is a slight gap to allow insects to fall in
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What is a quadrat?
A square made of wire. The organisms underneath can be identified and counted
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What is the use of a transect line?
The distribution of organisms can be mapped using a transect line. This data can be displayed as a kite diagram
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What is zonation?
Zonation is the gradual change in species distributed across a habitat
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What is capture-recapture?
You capture a sample of the population, mark the animals and release them. You then recapture another sample and see how many are marked
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Population size?
Number in 1st sample x Number in 2nd sample / Number in 2nd sample previously marked
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What assumptions are made with the capture-recapture method?
There are no deaths or reproductions and no movement on animals in and out of the area. Identical sampling methods are used for both sample. The markings have not affected the animals chance of survival
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What is photosynthesis?
Carbon dioxide + Water -> Glucose + Oxygen
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What are the two stages taking place in photosynthesis?
Water is split up by light energy releasing oxygen gas and hydrogen ions. Carbon dioxide combines with the hydrogen ions producing glucose and water
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Where does photosynthesis take place?
It takes place in chloroplasts in plant cells- they contain pigments like chlorophyll that absorb light energy
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What is glucose converted into?
Used in respiration, releasing energy. Converted into cellulose to make cell walls. Converted into proteins for growth and repair. Converted into starch, fats and oils for storage
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Why is starch used for storage?
This is because it is insoluble and does not move from storage areas. Unlike glucose, it does not affect the water concentration of cells and cause osmosis
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What increases the rate of photosynthesis?
More carbon dioxide. More light. A higher temperature which increases enzyme action
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What is meany by limiting factors?
Photosynthesis depends on light, temperature and carbon dioxide, a lack of one of these factors will limit the rate of photosynthesis
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How do plants respire?
Plants respire at all times by taking in oxygen and releasing carbon dioxide
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What did Greek scientists believe?
They believed that plants took minerals out of the soil to grow and gain mass
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What did Van Helmot conclude?
He concluded from his experiment on growing a willow tree that plant growth could not be due only to the uptake of soil minerals- it must depend on something else
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What did Priestley conclude?
He concluded from his experiment that plants produce oxygen
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How is the outer epidermis adapted for efficient photosynthesis?
The outer epidermis lacks chloroplasts and so is transparent; there are no barrier to the entry of light
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How is the upper palisade layer adapted for efficient photosynthesis?
The upper palisade layer contains most of the leaf's chloroplasts, as they will receive most of the light
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How are the spongy mesophyll cells adapted for efficient photosynthesis?
The spongy mesophyll cells are loosely spaced so that diffusion of gases between cells and the outside atmosphere can take place
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How is the arrangement of he spongy mesophyll cells adapted for efficient photosynthesis?
The arrangement of mesophyll cells creates a large surface area/volume ratio so that large amounts of gases can enter and exit the cells
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How are leaves adapted for efficient photosynthesis?
They are broad so that they have a large surface area to get as much light as possible. They are thin so that gases can diffuse through and light can get to all cells. They contain chlorophyll so that light from a broad range is used
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How are leaves adapted for efficient photosynthesis?
Vascular bundles for support and transport of chemicals such as water and glucose. Specialised guard cells which control the stomata therefore regulating the flow of carbon dioxide and oxygen as well as water loss
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Why is having many pigments beneficial?
This is beneficial as the plant cell can maximise the use of the Sun's energy. Each pigment absorbs light of different wavelength
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What is diffusion?
Diffusion is the net movement of particles in a gas or liquid from an area of high concentration to an area of low concentration, resulting from the random movement of particles
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How are leaves adapted to increase the rate of diffusion of oxygen and carbon dioxide?
A large surface area. Specialised openings called stomata, which are spaced out. Gaps between the spongy mesophyll cells
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How can the rate of diffusion increase?
A shorter distance for the molecules to travel. A steeper concentration gradient, A greater surface area for the molecules to diffuse from
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What is osmosis?
Osmosis is the movement of water across a partially permeable membrane from an area of high water concentration to an area of low water concentration
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What is a partially permeable membrane?
It is a membrane that allows the passage of water molecules but not large molecules like glucose
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What is the difference between a dilute and a concentrated solution?
A dilute solution has a high water concentration and a concentrated solution has a low water concentration
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What occurs during osmosis in plant cells?
The entry of water increases the pressure on the cell wall, which is rigid. The turgor pressure supports the cell, stopping it from collapsing, When too much water leaves a cell, it loses the pressure and the plant wilts
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What is meant by the terms turgid, flaccid and plasmolysed?
A plant cell full of water is said to be turgid. When the cell loses water, the pressure falls and the cell becomes flaccid. Eventually the cytoplasm begins to shrink and the membrane pulls away from cell wall- plasmolysed
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What occurs during osmosis in animal cells?
Since animal cells lack a supporting cell wall, when too much water enters they will swell up and burst- lysis. When too much water leaves an animal cell, it shows crenation by shrinking
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What is the role of xylem cells?
Xylem cells carry water and minerals from the roots to the leaves and are involved in transpiration
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What is the role of phloem cells?
Phloem cells carry food substances such as sugars up and down stems to growing and storage tissues- Translocation
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Properties of xylem cells?
Dead. No cytoplasm. Walls become thicker after growth. Lignified-strong. Loose nuclei. Cell end walls are digested and die when plant stops growing
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Properties of phloem cells?
Remain alive after plant growth. Not lignified. Sieve plates which allow movement of substances between cells
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What do root hairs produce?
They produce a large surface area for water uptake by osmosis
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What is transpiration?
Transpiration is the evaporation and diffusion of water from inside leaves. This loss of water from leaves helps to create a continuous flow of water from the roots to leaves in xylem cells
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What does transpiration ensure?
It ensures that plants have water for cooling by evaporation, photosynthesis and support from cells' turgor pressure and transport of minerals
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What increases the rate of transpiration?
Light intensity. Temperature. Air movement. Decrease in humidity
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How does an increase in light intensity increase the rate of transpiration?
The stomata close in the dark and open in the light. When light intensity is greater, more stomata will open. This allows more water to evaporate- increasing transpiration
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How does an increase in temperature increase the rate of transpiration?
The higher the temperature, the faster the particles will more. This means that water molecules move faster and evaporate quicke
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How does an increase in air movement increase the rate of transpiration?
It evaporates water molecules very quickly, which increases the diffusion of water out of leaf- increasing transpiration
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How does a decrease in humidity increase the rate of transpiration?
This allows water molecules to diffuse quicker, increasing the rate
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How is the structure of a leaf adapted to prevent water loss?
Having a waxy cuticle covering the outer epidermal cells and by most stomatal openings being situated on the shaded lower surface- slow down diffusion
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How is the structure of a leaf adapted to reduce water loss?
Guard cells are able to change size of stomatal openings. Guard cells contain chloroplasts, so photosynthesis produces sugars, increasing turgor pressure, causing the cell to swell. Fewer stomata. Smaller stomata. Position of stomata on underside
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Why do plants need nitrates?
To make proteins , which plants use for cell growth
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Why do plants need phosphates?
Involved in respiration and growth
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Why do plants need potassium compounds?
Involved in respiration and photosynthesis
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Why do plants need magnesium compounds?
Involved in photosynthesis
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What is nitrogen used to produce?
It is used to produce amino acids, which combine to form a variety of proteins
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What is phosphorus used to produce?
It is used to make DNA, which contains the plants genetic code, and cell membranes
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What is potassium used to produce?
It is used to help enzyme action in photosynthesis and respiration- speed up chemical reactions
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What is magnesium used to produce?
It is used to make chlorophyll, which is essential for photosynthesis
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What does a lack of nitrates cause?
Poor growth and yellow leaves
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What does a lack of phosphate cause?
Poor root growth and discoloured leaves
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What does a lack of potassium cause?
Poor flower, poor root growth and discoloured leaves
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What does a lack of magnesium cause?
Yellow leaves
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Where are minerals usually present?
In soil in low concentrations
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How are minerals taken up by root hair cells?
By active transport. A system of carriers transport selected minerals across the cell membrane
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What does active transport enable?
It enables minerals, present in the soil only in low concentrations, to enter root hairs already containing higher amounts of minerals
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What is a detritivore?
A detritivore feed on dead and decaying material (detritus). They increase the rate of decay by breaking up the detritus and so increase the surface area for further microbial breakdown
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What increases the rate of decay?
Increasing the temperature, amount of oxygen and water
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What happens when there is an increase in temperature?
Increasing the temperature to an optimum will increase the rate of respiration. Higher temperatures will denature enzymes
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What happens when there is an increase in oxygen?
By increasing the amount of oxygen, bacteria will use aerobic respiration to grow and reproduce faster
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What happens when there is an increase in water?
This will allow for material to be digested and absorbed more efficiently and increase growth and reproduction of bacteria and fungi
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What is a saprophyte?
This is an organism that feeds on dead and decaying material by releasing an enzyme, e.g. a fungus
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What is extracellular digestion?
Fungi produce enzymes to digest food outside their cells and then reabsorb the simple soluble substances
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What does food preservation do?
It reduces the rate of decay
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Examples of food preservation?
Canning-kills bacteria, Removes oxygen. Drying-no water for bacteria to grow. Freezing- kill bacteria, slow down growth. Pickling-acidic conditions kill bacteria and fungi. Jams-microbes lose water via osmosis
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What are the disadvantages of using pesticides?
They can enter and accumulate in food chains. They can harm other organisms living nearby which are not pests. Some are persistent (take a long time to break down and become harmless)
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What is organic farming?
Organic farming does not use artificial fertilisers or pesticides. it uses animal manure and compost instead
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What other techniques are used in organic farming?
Crop rotation- to avoid build up of soil pests. Nitrogen-fixing crops. Varying seed planting times to get a longer crop time
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Advantages and Disadvantages of organic farming?
A- healthier, tastier. D- smaller crops, expensive produce
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What is meany by biological control?
Biological control uses living organisms to control pests
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What problems has biological control caused?
The introduced species eating other useful species and then showing a rapid increase in their population so they themselves become pests and then spread into other areas
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What is intensive farming?
Intensive farming, which makes use of artificial pesticides and fertilisers, is very efficient in producing large crop yields cheaply
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Why do intensive farming methods raise concerns?
Raise concerns about animal cruelty, as animals are kept in small areas, and about the effects of extensive use of chemicals on soil structure and other organisms
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Why is intensive farming beneficial?
By keeping animals inside sheds (battery farming), they use less energy to keep warm and to move, and more energy on growth
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What are hydroponics?
Plants can be grown without using soil using hydroponics. This system uses a regulated recycling flow of aerated water containing minerals and is usually done in glasshouses, in areas of barren soil
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Why do hydroponics have a better control over mineral levels and disease?
As it is a soil-free system, many plants can be grown in a small space. As there is no anchorage for plants when using water, artificial fertilisers are used
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Card 4

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