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WJEC A Level Biology > Population size and ecosystems > Flashcards

Population size and ecosystems Flashcards

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1
Q

What is a fugitive species

A

Cannot tolerate competition. They reproduce rapidly and spread out. They are able to invade new environments rapidly

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2
Q

What is an equilibrium species

A

Control their population by competition in a stable habitat. Bacteria and rabbit populations show this type of growth

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3
Q

What is the birth rate

A

The reproductive capacity of a population; the number of new individuals derived from reproduction per unit of time

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4
Q

What is immigration

A

The movement of individuals into a population of the same species

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5
Q

What is a population

A

The number of organisms of the same species living within a given area.

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6
Q

What is the lag phase of a population growth chart

A

Population number increases very slowly because time is needed for enzyme synthesis

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7
Q

What is the exponential phase of a population growth chart

A

Plenty of nutrients and few toxic by-products so there a no limiting factors to reproduction and population size increases rapidly

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8
Q

What is the stationary phase of a population growth chart

A

Cells are reproducing but population is relatively constant as the rate of cell production = rate of cell death. The population has reached its carrying capacity because reduced resources and toxic by-products are now limiting factors

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9
Q

What is the death phase of a population growth chart

A

More cells are dying that being produced so the population decreases. Death of cells is due to lack of oxygen, nutrients or toxicity of the medium

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10
Q

What is the carrying capacity

A

the limit of a population, where the death rate is equal to the birth rate

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11
Q

What is a population crash

A

Sudden decrease in population number

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12
Q

What causes a population crash

A

When a population greatly increases its carrying capacity

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13
Q

What happens after a population crash

A

The set carrying capacity us much lower as the environment is usually damaged beyond repair

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14
Q

What is intraspecific competition

A

Competition within the same species

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15
Q

What is interspecific competition

A

Competition between different species

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16
Q

List factors that affect a population

A 
Food supply
Competition
Predation
Living space
Parasitism
Weather
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17
Q

What are biotic factors

A

Factors directly impacted by living things, eg. predation, disease and competition

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18
Q

What are abiotic factors

A

Factors that are not affected by living things, eg. temperature, O2/CO2 concentration, nutrient/water availability

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19
Q

Describe a predator-prey cycle

A

Predator peak is always lower than prey peak
Predator peak comes after prey peak
Occurs in a continuous cycle

20
Q

What is a population index

A

(birth rate + immigration) - (death rate + emigration)

21
Q

What are density dependant factors

A

Limit the carrying capacity as they weaken individuals and make them less likely to reproduce

22
Q

What are density independent factors

A

These are not linked to the population density, eg. natural disasters

23
Q

Explain mark, release recapture and tactics used to reduce its effect on the animals

A

Capturing an animal, marking it, and catching another load again every few hours. The way you mark them must be subtle otherwise it can inhibit their ability to catch prey or can increase their visibility an likelihood to be caught.

24
Q

What is a detrivore

A

feed on dead and decaying matter, increase surface area for saprophytes

25
Q

Why does only a little energy pass through each trophic level

A

some parts of the organism are inedible
some parts of the organism cannot be digested
heat energy lost via respiration

26
Q

What is gross primary productivity

A

the energy converted in plants into organic molecules

27
Q

What is net primary productivity

A

Plants use some of the energy in respiration, losing some as heat. The energy stored forms new biomass.

28
Q

Name disadvantages of pyramids of number

A

due to an often large number of organisms at the bottom it is almost impossible to draw to scale

29
Q

Name disadvantages of pyramids of biomass

A

This is very destructive as it requires killing organisms and so is generally considered unethical

30
Q

What is succession

A

gradual change over many years where plain ground goes from being empty to being able to grow more complex life

31
Q

What is a pioneer species

A

the first species to colonise a new area. They are usually very resistant to harsh abiotic factors

32
Q

What is a climax community

A

the most complex environment an area can grow to

33
Q

What is primary succession

A

the introduction of species to an area that was previously uninhabited

34
Q

What is secondary succession

A

the reintroduction of species into a bare habitat that was previously inhabited, ie, after a forest fire

35
Q

How does succession work

A

Each organism living there modifies the environment, usually improving soil quality and making more opportunities for other organisms to thrive

36
Q

What is a niche

A

the role and position a species has in its environment

37
Q

What are the stages of the nitrogen cycle

A

Deamination
Nitrification
Nitrogen Fixation
Denitrification

38
Q

How do plants obtain nitrates

A

From the soil by active transport

39
Q

Explain what happens in deamination and the product formed

A

Saprophytic bacteria break down dead and decaying matter. Breaking them down releases ammonia.
Nitrogen Compounds -> Ammonia

40
Q

Explain what happens in nitrification and the products formed

A

One type of nitrifying bacteria converts ammonia into nitrites, and another converts nitrites into nitrates.
Ammonia - > Nitrites -> Nitrates

41
Q

Explain what happens in nitrogen fixing and the product formed

A

Nodules on legume plants contain bacteria with which they have a mutualistic relationship. The bacteria make ammonia to be turned in nitrates by nitrifying bacteria.
Nitrogen -> Ammonia

42
Q

Explain what happens in denitrification and the product formed

A

Denitrifying bacteria in the soil convert nitrates back into nitrogen gas. This works against farmers who want to keep a maximum number of nitrates in the soil.
Nitrate -> Nitrogen gas

43
Q

Name the four processes in the carbon cycle

A

Photosynthesis
Respiration
Combustion
Decay

44
Q

How is carbon removed from the atmosphere

A

Photosynthesis removes CO2 from the atmosphere

45
Q

How is carbon returned to the atmosphere

A

Respiration - CO2 is a by-product of respiration
Combustion - CO2 is released from the combustion of fossil fuels
Decay - saprophytes break down organic molecules and release CO2

WJEC A Level Biology (16 decks)

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