Biology B4

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What is a population?
All the organisms of one species in a habitat
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What is a community?
Populations of different species in a habitat
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What is the capture-recapture method and how is it done?
It is a method of sampling that is used to estimate population size. Firstly you capture a sample of the population, mark the animals in a harmless way and then release them. Then you recapture another sample and count how many are marked
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How is population size estimated (capture-recapture)?
(no. in 1st sample x no. in 2nd sample)/ no. in 2nd sample previously marked
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What assumptions do we have to make about the capture re-capture method?
That there have been no deaths and immigration/emigration, the sample methods were identical and the marking hasn't affected the species chance of survival.
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What is a ecosystem and is it self-supporting?
An ecosystem is all the organisms living in a particular area, as well as the abiotic conditions. It is self-supporting
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How are transects carried out?
Firstly mark a line using a tape measure then place quadrats next to each other along the line. Finally count and record the organisms found in the quadrat
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What is percentage cover?
It is estimating the percentage of the quadrat that the organsim covers (count all the squares it fills up)
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What do kite diagrams show?
They show the abundance and distribution of organisms
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What are abiotic factors and how does it affect distribution?
It is all the non-living conditions (sunlight). It affects distribution as some organisms are adapted to live in certain physical conditions so they can't survive in certain areas. Also some organisms better adapted will out-compete them
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What is zonation?
The gradual change in the distribution of species across a habitat
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How is biodiversity measured (what does it include)?
The amount of variation between individuals of the same species in an area, the no. of species and habitats in an area
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How does bio-diversity affect eco-systems?
Eco-systems with a high level of biodiversity are healthier because they are better able to cope with changes in the environment
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Why are natural eco-systems better than artificial eco-systems?
Because they are more bio-diverse and are healthier eco-systems as there is no human interference?
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What are the reactants of photosynthesis (symbols)?
6CO2 + 6H20 (carbon dioxide and water)
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What are the products of photosynthesis (symbols)?
C6H12O6 + 602 (glucose and oxygen)
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What 2 things does water split into using light energy?
Hydrogen ions and oxygen gas
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What is glucose used for?
For respiration, making cell walls (cellulose), turned into lipids and stored in seeds, stored as starch and combines with nitrates from the soil to produce amino acids which are then made into proteins and used for growth and repair
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What did Van Helmont conclude from his experiments?
That plants gained mass by taking in water as well as minerals from the soil (Greek scientists). We now know that plants also gain mass by using CO2 from the air
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What did Priestley conclude from his experiments?
That the plants produced something (oxygen) that burning/ combustion and breathing/respiring took away from the air
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Name the three limiting factors of photosynthesis.
Light (intensity), carbon dioxide concentration, and the temperature
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Give the definition of diffusion.
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration
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Can proteins and starch pass through the cell membrane.
No, only small particles like simple sugar, water and ions can pass though
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What 3 things does the rate of diffusion depend on?
Distance, concentration difference (gradient) and surface area
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Where are the guard cells found on a leaf, and what is their function?
They are found at the bottom of the leaf and control when the stoma opens and closes
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Which cells contain most of the chloroplast and why?
The palisade cells because they are at the top and are exposed to the most sunlight. Therefore this maximizes the rate of photosynthesis
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What is special about the upper epidermis?
The upper epidermis is transparent so that light can pass through it to the palisade layer
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Name the 4 pigments found in plants.
Chlorophyll a, chlorophyll b, carotene and xanthophyll
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What are the 2 transport vessels called, and what is their function?
They are called xylem and phloem; the xylem transports water to the parts of the leaves and the phloem transports sugars/glucose to the other parts of the plant
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Why does a plant respire all the time?
To produce energy, which is needed for the plant to survive
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What is the internal surface area to volume ratio of a plant?
Plants have a very big internal surface area to volume ratio
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What is the definition of osmosis?
Osmosis is the net movement of water molecules across a partially permeable membrane from an area of higher water concentration (dilute solution) to an area of lower water concentration (concentrated solution)
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Why is it called net movement?
It is called net movement because the particles move randomly in both directions but because there are more particles on one side of the membrane, there is an overall movement from that side
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Describe what happens to a plant cell when the plant is short of water and has plenty of water.
When the plant has plenty of water the cell becomes swollen and becomes turgid, when the plant doesn't have enough water the cell droops and becomes flaccid and when the plant is really short of water the cell becomes plasmolysed
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What happens if an animal cell if it absorbs too much water and not enough water?
When the cell doesn't absorb enough water the cell shrivels up and this is known as crenation. When it absorbs too much water it bursts and this is known as lysis
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What do phloem tubes do?
They transport food substances up and down the stem to growing and storage tissues.
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What do xylem vessels do?
They transport water up the stem.
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What are xylem vessels made of?
They are made with dead cells joined end to end.
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What are the 3 types of cross-sections that phloem and xylem are found in?
Root, stem and leaf cross-section.
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Why do roots have hairs?
To give the plant a bigger surface area to absorb more water.
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Name the process that root hairs take water in by.
Osmosis because there is usually a higher concentration of water in the soil than the inside of the plant.
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Describe the transpiration stream.
Water evaporates and diffuses out of leaf due to transpiration and so due the the lack of water in the leaf the plant takes up more water from the soil, through its xylem vessels. This water evaporates and diffuses out of the leaf. This continues.
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Name the 4 factors that affect the transpiration rate.
Light intensity, temperature, air movement and air humidity.
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Name some plant adaptations that help reduce water loss.
Leaves have a waxy cuticle, most stomata are found at the bottom of the leaf (where it is cooler), some plants which live in hot climates have smaller stomata.
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What happens to the guard cell when the stoma opens and closes?
When the guard cell become turgid, the stoma opens. When the guard cell become flaccid, the stoma closes.
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Name the 3 minerals needed for a healthy growth.
Nitrates, Phosphates and Potassium.
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What is potassium needed for and what are the deficiency symptoms?
To help enzymes needed for photosynthesis and respiration. If there is insufficient potassium, plants have poor flower and plant growth and discoloured leaves.
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What is active transport?
Active transport uses energy from respiration to help the plant pull minerals into the root hair, against the concentration gradient (low concentration to high concentration).
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What 3 things affect the rate of decay?
Temperature, amount of water and amount of oxygen
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Give at least 2 examples of detrivores.
Earthworms, maggots and woodlice.
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Give at least 1 example of a saprophyte.
Fungi and bacteria.
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What is extracellular digestion and which type of decay organism does this?
Saprophytes do this. It is when they feed by releasing enzymes onto the material outside of their cells. The enzymes break down the material into smaller bits; which can then be absorbed by saprophytes.
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Give at least 3 examples of preservation.
Canning, cooling, freezing, drying, adding salt/sugar and adding vinegar (pickling).
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Define intensive farming.
It is trying to produce as much food as possible from your land, animals and plants.
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How can pesticides have bad effects further along the food chain?
There is a danger of the pesticide being passed down the food chain, and since most pesticides are not removed even when animals excreted, it's passed along the chain. Usually the concentration of the pesticide increases becoming even more dangerous.
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What is biological control? Name one method.
Biological control is using living things instead of chemicals to control a pest. One method is using predators. You could also use parasites or a disease. For example ladybirds are used to control aphids as they are predators of it.
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What are 2 advantages of biological control?
The advantages are that there is no need to keep on repeating the treatment and less pesticides are used (so there is less pollution and also it doesn't disrupt the food chain as much).
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What are 3 disadvantages of biological control?
The disadvantages are that the predator introduced might not eat the pest, the predator/parasite population might get out of control and they might end up becoming the pest and the predator might end up flying away/running away.
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Name 4 techniques used in organic farming.
Organic fertilisers (which recycles the nutrients in plant and animal waste) is used, crop rotation (nitrogen fixing beans) is done, weeding is carried out by hand and biological control.
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Name 2 advantages of organic farming.
Organic farming uses less chemicals (less risk of chemicals remaining on food) and it's better for the environment.
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Name 2 disadvantages of organic farming.
Organic farming is more labour intensive so it costs more and it also takes up more space (less space for wildlife, etc.).
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Card 2


What is a community?


Populations of different species in a habitat

Card 3


What is the capture-recapture method and how is it done?


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Card 4


How is population size estimated (capture-recapture)?


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Card 5


What assumptions do we have to make about the capture re-capture method?


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