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107 Cards in this Set

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Explain how you can estimate population sizes using capture-recapture

1. Capture a sample of population, mark them in a harmless way
2. Release them
3. Recapture another sample and count how many are marked
4. Estimate using equation
What is the capture recapture equation?
Number in 1st sample x Number in 2nd
Number in 2nd previously marked
How do you estimate a population size using quadrats?
1. Count all the organisms in a 1m squared quadrat
2. Multiply it by the total area of the habitat
What assumptions must be made with capture recapture? (3 points)
- No deaths, immigration or emigration
- Captured in the same way
- Marking doesn't affect their chance of survival
What is an eco-system?
All the organisms living in a particular area as well as the non-living (abiotic) factors
What is a habitat?
An area where an organism lives
What is meant by eco-systems being self-supporting?
They contain almost everything they need to maintain themselves
What is distribution?
Where organisms are found within a particular area
How do you carry out a transect to investigate distribution?
Measure out a line using a tape measure and place quadrats next to each other along the line.
Count and record the organisms in the quadrat
Why is the distribution of organisms affected by abiotic factors?
- Organisms are adapted to live in certain conditions. Meaning they are more likely to survive and reproduce in these conditions.
- Many organisms can only survive in the conditions they're adapted to
What is zonation?
The gradual change in the distribution of species across a habitat
What is biodiversity?
A measure of the variety of life in an area
What 3 things does biodiversity include?
- Amount of variation between individuals of the same species in an area
- The number of different species in an area
- The number of different habitats in an area
Why is biodiversity important?
Eco-systems with a high level of biodiversity are healthier because more diverse ecosystems are better able to cope with changes in the environment
What is a natural ecosystem? Give two examples
Maintain themselves without any major influence from humans eg. native woodlands and natural lakes
What is an artificial ecosystem? Give two examples
Created and maintained by humands Eg. forestry plantations and fish farms
Why do native woodlands have a higher biodiversity than forestry plantations?
(Tree species, age, plant species, habitats, animals)
- Variety of tree species VS one tree species
- Different ages and sizes of trees VS planted at same time = same age
- Variety of plant species VS fewer plant species (trees and densley planted, limited light and space)
- Variety of habitats VS fewer habitats (aren't enough plants to create them and cutting down trees destroys them
- Variety of animals VS fewer (there aren't many habitats or sources of food)
Why do lakes have a higher biodiversity than lakes?
- Many fish species VS one (farmed for food)
- Variety of plants VS fewer (fish food is added, waste creates an algal bloom = blocks light)
- Variety of animal species VS fewer (predators kept out, pests killed, less food and fewer habitats bc lack of plants)
What is photosynthesis?
Uses energy from the sun to change carbon dioxide and water into glucose and oxygen
Where does photosynthesis take place? Why does it take place here?
In the chloroplasts of plant cells
Contain pigments like chlorophyll that absorb light energy
What is the balanced symbol equation for photosynthesis?
6CO(2) + 6H(2)O = C(6) H(12) O(6) + 6O(2)
What are the two stages of photosynthesis?
- Light energy splits water into oxygen and hydrogen ions
- Carbon dioxide combines with hydrogen ions to make glucose and water
Give 5 ways plants use the glucose they make
1. Stored in seeds
2. Making cell walls
3. Stored as starch
4. For respiration
5. Making proteins for growth and repair
How is glucose used for making cell walls?
Glucose is converted into cellulose for making cells walls
How is glucose stored as starch and why?
It is turned into starch and stored in roots, stems and leaves ready for use when photosythesis isn't happening eg. at night
How is glucose used to make proteins?
Glucose is combined with nitrates to make amino acids which are then made into proteins for growth and repair
Why do plants use glucose for respiration?
It releases energy so they can convert the rest of the glucose into various other useful substances
How is glucose stored in seeds?
It is turned into lipids (fats and oils) for stroing in seeds
Why is starch good for storage?
- It doesn't dissolve in water and move away in solution
- It doesn't affect water concentration
What did Greek scientists conclude about plant growth?
Observed that the only thing touching the plants was the soil, so they decided plants must gain mass by taking in minerals from the soil
What did Van Helmont conclude about how plants gained mass?
Experiment: Dried soil, weighed it, planted a tree, added rain water whenever it was dry
- 5 years later, the plant had gained 74.5kg of mass
- Dried the soil and weight it, and had changed little
- Concluded that water gained mass by taking in water
What did Priestly's experiment involving a candle show?
1. Candle in a sealed container = flame went out after short time and couldn't be relit
2. Candle in a sealed container and a plant = flame went out but after a few weeks could be relit
He decided the candle used something in the container up, and the plant "restored the air"
What did Priestly's experiment involving a mouse show?
1. Exhaled air in sealed container = mouse died after a few seconds
2. Living plant and exhaled air = mouse put in a few days later and the mouse survived for several minutes
Mouse couldnt survive because breathing had taken something out of the air, and the plant "restored" it
How did scientists find out where the oxygen released in photosynthesis came from?
1) Supplied plants with water containing an isotope of oxygen called oxygen-18
2) The carbon dioxide the plants recieved contained ordinary oxygen-16
3) The plants release oxygen-18 showing that the oxygen came from the water
What are the 3 limiting factors of photosynthesis?
1) Light intensity
2) Carbon dioxide
3) Temperature
How does light intensity affect photosynthesis?
The rate of photosynthesis increases but only to a certain point, after that the temperature or CO(2) level is now the limiting factor
How does the carbon dioxide level affect photosynthesis?
The rate increases but only to a certain point, after that the temperature of light intensity is the limiting factor
How does temperature affect photosynthesis?
As temperature increases, the rate of photosynthesis increases
But if too high = plants enzymes denature and so rate rapidly decreases
What is diffusion?
The net movement of particles from an area of high concentration to an area of low concentration
What does the rate of diffusion depend on?
1) Diffusion distance: shorter distance = faster
2) Concentration difference: larger difference = move across
3) Surface area: more surface = faster
What molecules diffuse through cell membranes?
Simple sugars, water or ions
What two processes do plants carry out?
Respiration and photosynthesis
What do plants release and take in during the day?
Take in = carbon dioxide
Release = oxygen
What do plants release and take in during the night?
Why do they do this?
Take in = oxygen
Release carbon dioxide

They cannot photosynthesise during the night, only respire
Explain the diffusion of gases during the day (photosynthesis) in plant leaves
1) Uses up lots of CO(2) in photosynthesis = little in leaf
2) Makes more CO(2) diffuse into the leaf
3) Lots of O(2) is being made as a waste product of photosynthesis
4) Some is used in respiration, the rest diffuses out
Explain the diffusion of gases during the night (respiration) in plant leaves
1) No photosynthesis happening so there is lots of CO(2) from respiration and lots of O(2) is used up
2) Lots of CO(2) diffuses out and lots of O(2) diffusing in
Explain 5 ways that leaves are adapted for diffusion
1) Broad: Large surface area
2) Thin: Short diffusion distance
3) Stomata: little holes that let gases in and out
4) Guard cells: control gas exchange by controlling opening and closing of stomata
5) Air spaces in spongy mesophyll layer: Allows gases to move between stomata and photosynthesising cells, large SA for gas exchange
Explain 5 ways that leaves are adapted to absorb light
1) Broad: Large surface area exposed to light
2) Contain lots of chloroplasts: contain chlorophyll and other photosynthesis pigments to absorb light energy
3) Different pigments absorb different wavelengths = make the most of the energy by absorbing as much as possible
4) Palisade layer near the top of the leaf contains most chloroplasts
5) Upper epidermis is transparent so light can pass to the palisade layer
What is osmosis?
The net movement of water molecules across a partially permeable membrane from a region of high concentration to a region of low concentration
Why do water molecules pass both ways through a membrance?
Water molecules move about randomly all the time
What is turgor pressure?
- When the contents of the cell push against the inelastic cell wall
- Helps support the plant tissues
What does turgid mean?
When the plants cells have drawn in water by osmosis and become plump and swollen
What does flaccid mean?
When a plant wilts because the cells start to lose water and so lose their turger pressure
What does it mean when a cell becomes plasmolysed?
When the cytoplsm inside the cell starts to shrink and the membrane pulls away from the cell wall
Why doesn't a plant completely lose its shape when it becomes plasmolysed
Because the inelastic cell wall keeps things in position
What happens if an animal cell takes in too much water?
It bursts (lysis)
What happens if an animal cell loses too much water?
It shrivells up (crenation
What are phloem tubes made of?
Columns of living cells with perforated end-plates to allow stuff to flow through
What do phloem tubes transport?
Food substances (mainly sugars) both up and down the stem to growing and storage tissues
What is the movement of food substances around a plant called?
What are xylem vessels made of?
- Dead cells joined end to end with no end walls between them and a hole (lumen down the middle).
- Thick sides are made of cellulose
Why are the thick side walls made of cellulose?
Strong and stiff to support the plant
What do xylem vessels transport?
Water and minerals from the roots up the shoort to the leaves in the transpiration stream
How do plants taken in water by osmosis? Why?
Root hair cells
- Give plant a large surface area for absorbing water from the soil
Explain transpiration
1) Evaportation and diffusion of water vapour from inside the leaves
2) Causes a shortage of water in the leaf, so more is draw up through the xylem vessels to replace it
3) Means there is a constant transpiration stream as water is drawn up from the roots
What 4 advantages does the transpiration stream have for a plant?
1) Keeps plant cool
2) Provides constant water supply for photosynthesis
3) Water creates turgor pressure to support the plant
4) Minerals are broughout up from the soil along with the water
What 4 things increase the rate of transpiration?
1) Increase in light intensity
2) Increase in temperature
3) Increase in air movement (wind)
4) A decrease in air humidity
What 3 adaptations do plants have to reduce water loss?
1) Leaves have waxy cuticle covering the upper epidermis = makes upper layer of leaf waterproof
2) Most stomata are found on the lower surface of the leaf where it is darker and cooler. Helps slow down diffusion of water out of leaf
3) Smaller and fewer stomata
What happens when the guard cells are turgid?
The stoma opens
What happens when the guard cells are flaccid?
The stoma closes
What three main minerals do plants need?
1) Nitrates
2) Phosphates
3) Potassium
What are they needed for?
What happens if a plant doesn't recieve enough nitrates?
1) Contain nitrogen for making amino acids and proteins for cell growth
2) It's growth will be poor and it will have yellow older leaves
What are they needed for?
What happens if a plant doesn't recieve enough phosphates?
1) Contain phosphorous for making DNA and cell membrances. For respiration and growth
2) Poor root growth and discolored older leaves
What are they needed for?
What happens if a plant doesn't recieve enough potassium?
1) To help enzymes needed for photosynthesis and respiration
2) Poor flower and fruit growth and discoloured leaves
Why do plants need magnesium? What happens if a plant doesn't recieve enough magnesium?
1) It is required for making chlorophyll (for photosynthesis)
2) Yellow leaves
How do root hair cells take in minerals?
Using active transport
What is active transport?
Uses energy from respiration to help the plant pull minerals into the root hair against the concentration gradient
Why is active transport used?
The concentration of minerals in the soil is usually lower than in the root hair cell
What 3 things does the rate of decay depend on?
1) Temperature
2) Amount of water
3) Amount of oxygen
Why does the temperature effect the rate of decay?
A warm temperature makes things decay faster because it speeds up respiration in micoorganisms
Why does the amount of water effect the rate of decay?
Things decay faster when they're moist because microoganisms need water
Why does the amount of oxygen effect the rate of decay?
Decay is faster because the microorganisms can respirate aerobically, providing more energy
What are detritivores?
- Feed on dead and decaying material (detritus)
- They break it into smaller bits to give a bigger surface area for smaller decomposers to work on and so speeds up decay
Eg. Earthworms, maggots, woodlice
What are saprophytes?
- Feed on decaying material but do so by extracellular digestion
- They secrete disgestive enzymes which break it down and are then absorbed by the saprophyte
Eg. Fungi
What are 6 ways to slow down the rate of decay of food?
1) Canning: Keeps decomposers out
2) Cooling: Slows down the decomposers rate of reproduction
3): Freezing: Decomposers can't repoduce at low temperatues
4) Drying: Decomposers need water to carry out cell reactions
5) Adding salt/sugar: Decomposers will lose water by osmosis so they cannot work properly
6) Adding vinegar: Acid kills decomposers
What is intensive farming?
Trying to produce as much food as possible from land, animals and plants
What 3 methods are used in intensive farming?
1) Herbicides
2) Pesticides
3) Battery farming animals
Why do farmers use herbicides?
Kill weeds
- More energy from the Sun goes to crops and not on competing plants
Why do farmers use pesticides?
Kill pests
- Ensure no energy is transferred into a different food chain
Why do farmers use battery farming?
Animals are kept close together in small pens
- Warm and can't move about so less energy is used/wasted
What is hydroponics?
When plants are gorwn in nutrient solutions instead of soil
What are 2 advantages of hydroponics?
Control disease
Mineral levels controlled accurately
What are 2 disadvantages of hydroponics?
Lots of fertilisers need to be added
No soil to anchor the roots and support the plants
Give 4 ways in which intensive farming can damage the environment
1) Removal of hedges: destroys habitats and can lead to soil erosion
2) Fetilisers can cause eutrophication
3) Pesticides disturb food chains
4) Battery farming is cruel
How do pesticides disturb food chains?
- Can kill organisms that aren't pests
- Can cause a shortage of food further up food chain
- Persistant and don't break down
- Toxic build up kills organisms higher up in food chains
What is biological control?
Using living things instead of chemicals to control a pest
Eg. A predator, a parasite or a disease
What are 2 advantages of biological control?
- No chemicals used: less pollution, disruption of food chains and risk to people eating food
- No need to reapply treatment as they reproduce
What are 4 disadvantages of biological control?
- It may move away from the area
- It may eat a useful species
- The population may get out on control
- Might not eat the pest
Give an example of a predator used to remove pests
Ladybirds are aphid predators so people release them into their fields/gardens to prevent roses and vegetables being eaten
Give an example of a disease used to kill pests
Myxomatosis used to kill rabits
Used in Australia as the rabbit population grew out of control and ruined crops
Give 5 methods of organic farming
- Organic fertilisers
- Crop rotation
- Weeding
- Varying seed plantation times
- Biological control
Why are organic fertilisers used?
Recycles nutrients left in plant/animals waste
Better for the environment (but not as effective)
Explain crop rotation
Growing a cycle of diffrent crops in a field each year
- Stops pests and diseases of one crop building up and stops nutrients running out
Explain weeding
Physically removing weeks rather than using herbicides
No chemicals involved but is more labour intensive
Explain varying seed plantation times
Sowing seeds later or earlier in the season to avoid major pest lifecycles so pesticides don't have to be used
What are 2 advantages of organic farming methods?
1) Fewer chemicals
2) Better for the environment: less pollution of rivers/disruption of food chains
What are 3 disadvantages of organic farming methods?
1) Takes up more space
2) More labour intensive: food more expensive
3) Can't grow as much food