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AQA A level Biology > Ecology > Flashcards

Ecology Flashcards

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1
Q

Define habitat

A

the place where an organism lives (characterised by physical conditions and the other organisms present)

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2
Q

Define population

A

all of the organisms of one species within a habitat

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3
Q

Define community

A

all of the populations of different species in a habitat at the same time (eg. in an oak woodland it might consist of aphids, earthworms, fungi, blue tits and oak trees)

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4
Q

Define ecosystem

A

a community of interacting organisms and their physical environment
plus all of the abiotic factors of its environment

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5
Q

Define abiotic conditions

A

all non-living features of an ecosystem

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6
Q

Define biotic conditions

A

all the living features of an ecosystem

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7
Q

Examples of abiotic conditions (2)

A

temperature, rainfall

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8
Q

Examples of biotic conditions (2)

A

predation and competition

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9
Q

Define ecological niche

A

The role of a species within its habitat and how the organism fits into the environment (where it lives, what it does there, what food it requires and how it obtains it, when it feeds, relationship to other living things, all the biotic and abiotic factors a species is adapted to)

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10
Q

Define adaption

A

a feature of an organism that increases its chances of survival and reproduction

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11
Q

Two major process to consider within an ecosystem

A

1) the flow of energy through the system

2) the cycle of elements through the system

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12
Q

Define carrying capacity

A

the particular maximum stable size of a population of species which an ecosystem can support

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13
Q

What does the carrying capacity of an ecosystem depend on?

A
  • the effect of abiotic factors (eg. if temp is cold the maximum may still be a v small population)
  • interaction between different organisms (intraspecific, interspecific competition and predation)
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14
Q

Define intraspecific competition

A

organisms of the same species compete with each other for the same resources

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15
Q

Define interspecific competition

A

organisms of different species compete with each other for the same resources (eg. red vs grey squirrel in the UK)

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16
Q

Define microhabitat

A

Smaller units within a habitat each with their own microclimate.

Within an ecosystem are many habitats and within these are many microhabitats. Eg. in an oak woodland a stream is one habitat and the mud at the bottom is the microhabitat of a bloodworm

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17
Q

Define the competitive exclusion principle

A

when no two species occupy exactly the same niche

‘two species competing for the same limited resource cannot coexist at constant population values.’

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18
Q

Define ecology

A

the study of inter-relationships between organisms and their environment

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19
Q

What is the difference between a habitat and niche?

A

a habitat is where it lives, a niche is what it does in its habitat

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20
Q

Maximum number of species that can occupy a niche?

A

1 only

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21
Q

What happens if two species attempt to occupy the same niche?

A

they will compete with each other and one species will be more successful until there is only one species left.

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22
Q

It may look like two species are occupying the same niche but…

A

there will be slight differences in how they live in the niche (eg. variations in what they eat)

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23
Q

Three types of adaption?

A

1) Behavioural - way the organism acts
2) Physiological - processes inside their body
3) Anatomical - structural features of their body

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24
Q

Define population size

A

the total number of individuals of one species in a habitat

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25
Q

What can populations be characterised as?

A

Dynamic. They vary in size and composition over time.

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26
Q

When can a population growth curve be plotted? And when can it not? - what should be done instead?

A

When a population changes in size slowly over a period of time. Not when a population size changes rapidly over a short period of time (eg. microorganisms such as bacteria). Instead, a logarithmic scale can be used so that the curve fits on the graph.

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27
Q

When will a population grow?

A

When there are no limiting factors

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28
Q

What are limiting factors which could result in the growth of a bacterial population slowing, diminishing or ceasing (4)

A
  • mineral ions are consumed as population increases
  • population becomes so large that bacteria at the surface prevent light reaching bacteria at deeper levels
  • other species introduced to the habitat (carried by animals or wind) and may feed on the bacteria or compete for light, food or minerals.
  • winter bringing lower temperatures, lower light intensity or shorter light duration
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29
Q

What changes the rate of growth of a population?

A

changes in abiotic or biotic factors

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30
Q

Name factors which can limit the growth of a population (8)

A
  • availability of Food, Light, Oxygen, Water and Shelter
  • accumulation of toxic waste
  • disease, predators
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31
Q

What is carrying capacity determined by?

A

Limiting factors

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32
Q

Three adaptions to abiotic factors

A

1) otters have webbed paws so they can swim and walk on land - can live and hunt on land and water which increases chances of survival and reproduction
2) seals have thick layer of blubber so can keep warm in cold seas - can live in places where although it is cold the food is plentiful so increases chances of survival and reproduction
3) hedgehogs hibernate and lower their metabolic rate during winter - conserves energy for coldest months so increases chances of survival and reproduction

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33
Q

Three adaptions to biotic factors

A

1) sea otters use rocks to smash open shellfish - access to another source of food so increases chances of survival and reproduction
2) male frogs have special mating calls to attract females - ensures they attract a mate of the same species - makes successful mating more likely so increases chances of reproduction
3) bacteria produce antibiotics that kill bacteria in the same area - less competition for resources so increases chances of survival and reproduction

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34
Q

What happens to population size when the temperature is not ideal for metabolic reactions of a mammal to take place?

A

The mammal spends more energy trying to maintain the correct body temperature. This means less energy is available for growth and reproduction so the population size will decrease.

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35
Q

How is population size affected by interspecific competition?

A

When two different species are competing with each other for the same resources the resources available to both populations are reduced.

Eg. if they share the same food there will be less food available to both species which means less energy for growth and reproduction so population size decreases in both species.

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36
Q

How do adaptions effect population size?

A

If two species are competing for resources but one is better adapted to the surroundings, the less well adapted species will be outcompeted.

Eg. grey squirrels are larger and can store more fat and eat a wider rage of food so this helps them to survive and reproduce more than red squirrels who they outcompete.

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37
Q

Describe and explain a graph showing intraspecific competition (number of individuals against time)

A
  • sideways S

1) population of a species when resources are plentiful. As population increases more individuals are competing for the same amount of space and food
2) Eventually there are limiting factors such as availability of food and space. There isn’t enough for all individuals so population declines
3) Smaller population again means less competition for space and food so more chance of growth and survival so population increases again

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38
Q

Describe a predator-prey population graph

A

(graph goes up and down)

………As prey population increases there is more food for predators so predator population increases

As predator population increases more prey is eaten so prey population decreases

As prey population decreases less food for predators so predator population decreases.

As predator population decreases prey population increases because more survive and are able to reproduce …….

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39
Q

Give an example of other factors involving predator-prey population sizes.

A

X declines because food availability is a limiting factor. But then predation on X by Y accelerates the declining population.

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40
Q

What are predator-prey population sizes described as?

A

interlinked (as one changes, the other changes)

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41
Q

What abiotic factors influence the size of a population?

A

1) temperature
2) light
3) pH
4) water availability
5) humidity

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42
Q

Explain why too high or low temperatures affect population carrying capacity?

A

Plants & cold blooded animals:
- too high temperatures enzyme denaturation reduces growth and chances of survival and reproduction. So population has smaller carrying capacity (of those with adaptions to live in higher temperatures)

  • too low temperatures enzymes work slowly metabolic rate reduced so less growth and chances of survival and reproduction.

Warm blooded animals:
- energy spent maintaining optimum body temperature so less energy for growth, mature more slowly and reproductive rate slows. Carrying capacity of warm blooded population at high/low temps is reduced.

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43
Q

Explain how light affects population carrying capacity?

A

lots of light = more photosynthesis = plants grown and more chance of survival and reproduction (more seeds produced etc). Increases carrying capacity of animals that feed on plants because more food.

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44
Q

What happens if abiotic factors are below the optimum for a population?

A

Fewer individuals able to survive because their adaptions are not suited to the conditions.

If no individuals have adaptions that allow for survival then the population becomes extinct.

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45
Q

Give 2 examples of intraspecific competition leading to reduced populations.

A

1) oak trees competing for resources. Some oak trees grow larger restricting light and taking water and minerals until eventually a population is reduced to a few dominant oaks.
2) robins compete for breeding territory. Female robins mate with males that have established territories to provide adequate food for a family. As resources lower each male must have a large territory to provide the same adequate amount of food. So fewer territories in a given area so less breeding pairs leading to a reduced population.

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46
Q

How could an increase in food supply effect population size?

A

more individuals likely to survive so increased probability that they will produce offspring and population size will increase

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47
Q

What type of relationship is a predator-prey relationship?

A

interspecific

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48
Q

How have predators and prey evolved?

A

alongside each other - as predators become faster, prey have got more protective features etc

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49
Q

Name for predators of plants

A

herbivores

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50
Q

What happens when there is a selection pressure on a population?

A

organisms with suitable adaptions survive and reproduce so the population evolves to be better adapted to the prevailing conditions.

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51
Q

Define abundance

A

the number of individuals of a species in a given space

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52
Q

Why are only small samples of a habitat studied?

A
  • time consuming to count all organisms

- damage to habitat studied if did so

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53
Q

Name two sampling techniques used to study habitats

A

1) random sampling (frame or point quadrats)

2) systematic sampling along belt transect

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54
Q

What are point quadrats and how are they used?

A
  • horizontal bar, two legs, ten holes at set intervals through each a pin is dropped
  • each species the pin touches is recorded
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55
Q

What are frame quadrats and how are they used?

A
  • square frame divided by string or wire into equally sized subdivisions
  • abundance of species counted in each frame
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56
Q

Three factors to consider when using quadrats

A

1) size of quadrat
2) number of quadrat samples taken
3) position of each quadrat within sample area (random sampling)

57
Q

where a population of species is not evenly distributed what size quadrat is best to use and why?

A

lots of small quadrats as this give a more representative result rather than a few large ones

58
Q

How many quadrats are a good amount?

A
  • larger number of sample quadrats the more reliable results will be
59
Q

Why is random sampling important?

A

avoids bias and ensures data is reliable

60
Q

How to carry out random sampling?

A
  • lat out two tape measures perpendicular to each other along area you want to study
  • obtain random coordinates from random number generator
  • place top left corner of quadrat at the coordinate and record number of species inside
61
Q

When might a belt transect be used?

A

When some form of gradual change in the communities of plants or animals occurs

(eg. distribution of organisms along a line of succession from the sea through sand dunes to woodland)

62
Q

How is a belt transect used?

A
  • lay tape across ground in a straight line
  • lay frame quadrat beside and record number of species
  • move quadrat along transect (by its own length) and repeat process
63
Q

What does random sampling with quadrats and the use of belt transects obtain?

A

measures of abundance of species

64
Q

How do we obtain reliable results when using a quadrat?

A
  • large sample size (many quadrats used)

- mean of all samples is calculated

65
Q

Why do we take lost of samples when using qudrats?

A

more representative of the whole community

66
Q

Two ways to measure abundance of species in a quadrat? + advantages & disadvantages

A

1) frequency (likelihood of specific species occurring in quadrat)
adv: useful when species are hard to count eg. grass, gives quick idea of general distribution
disadv: no info on density and detailed distribution of species

2) percentage cover (estimate of area of quadrat species covers)
adv: useful when species is v abundant or difficult to count, data collected rapidly and individual species need not be counted
disadv: less useful when organisms occur in overlapping layers (eg. plants)

67
Q

How do we measure the abundance of motile species?

A

mark-release-recapture technique

68
Q

What is the equation for the mark-release-recapture technique?

A

estimated population size = total no. individuals in 1st sample x total no. individuals in 2nd sample/ total number of marked individuals recaptured

69
Q

How to carry out a mark-release capture technique?

A

Capture a sample of individuals, count them then mark them all.

Release them back into the environment and recapture another sample a week later.

Count the number of total individuals in this sample and also the number of marked individuals in this sample.

Use this formula: estimated population size = no. Individuals in 1st sample x no. Individuals in 2nd sample/ no. recaptured individuals.

70
Q

What does the mark-release-capture technique assume? (6)

A

1) proportion of marked to unmarked individuals in the 2nd sample is the same as the proportion of marked to unmarked individuals in the whole population
2) The marked individuals released from the first sample distribute themselves evenly among the remaining population and have enough time to do this
3) There is no immigration into or emigration out of the population
4) There are few deaths and births in the population
5) method of marking is not toxic and does not make the individual more visible and therefore more liable to predation
6) The mark/label isn’t lost or rubbed off during the investigation

71
Q

When repeating investigation into population size, what does repeating the experiment do?

A

reduces likelihood that results are due to chance

72
Q

When using frame quadrats how can we estimate the number of individuals in the whole area?

A

mean of data collected in each sample x number of quadrats that fit into the whole area

73
Q

What type of organisms are quadrats and transects used to investigate?

A

non-motile organisms

74
Q

What is an interrupted belt transect?

A

When quadrats are placed at intervals along a belt transect (ie. spaces between each placement) in order to cover a larger distance.

75
Q

What are non-motile species called?

A

sessile species

76
Q

Define succession

A

the progression of an ecosystem as it changes over time

77
Q

In stages of succession, how many the introduction of species alter the environment?

A

1) make it less suitable for existing species. As a result the new species may out-compete the existing species.
2) make it more suitable for other species with different adaptations. As a result the species now with better adaptions may out-compete the new introduced species.

78
Q

What happens when alterations to the abiotic environment result in a less hostile environment?

A
  • species more likely to survive and reproduce
  • new communities form
    biodiversity changes/increases
79
Q

Primary succession

A

occurs when land is newly formed or exposed (Eg. volcanic eruption exposing new bare rock or sea level drops to expose a new area of land)
- can’t be any soil or organic matter (must be like bare rock)

80
Q

Secondary succession

A

occurs on land that has been cleared of all plants but the soil still remains (eg. a forest fire or forest being cut by humans)

81
Q

Define pioneer species

A

the first species to colonise a new land surface which is usually quite an inhospitable environment (eg. rock or land destroyed by fire)

82
Q

Describe primary succession

4 parts

A
  • pioneer species colonise the area. The abiotic conditions are harsh but the pioneer species have adaptions to cope with them. (eg. marram grass long roots to reach sea water + can tolerate salty water)
  • the pioneer species change the abiotic conditions; they die and their dead organic matter (humus) is decomposed by microorganisms forming a basic soil
  • this makes abiotic conditions less hostile. (eg. basic soil retains water). New organisms with different adaptions can move in and grow. These die and are decomposed bringing more dead organic material making the soil deeper and richer in minerals. Larger plants (eg. shrubs) can now grow because the soil is deeper and retains more water.
  • some of the new species may change the environment so it becomes less suitable for previous species. (eg. sand sedge stabilises sand through growth of rhizomes (underground stems) but marram needs free sand to constantly be reburried.
83
Q

Describe secondary succession

A
  • occurs in the same way as primary succession however there is already a soil layer
  • succession starts at a later stage and the pioneer species are larger plants
84
Q

Define climax community?

A

The final stage of succession when the ecosystem is supporting the largest and most complex community of plants and animals at a steady state where it remains stable over along period of time.

85
Q

Define dominant species

A

plants or animals that are better adapted to the improved conditions and therefore out-compete the plants and animals already there

86
Q

What happens as succession goes on?

A

the ecosystem becomes more complex, biodiversity increases

87
Q

Name examples of features of pioneer species that suit them to colonisation (6 things)

DENAPS

A

DENAPS - dormancy, extreme, nitrogen, asexual, photosynthesis, seeds

1) asexual reproduction so single organisms rapidly reproduces to build population quickly
2) production of large amounts of wind dispersed spores or seeds that can easily reach other isolated areas to colonise
3) seeds which don’t require a period of dormancy so they rapidly germinate on arrival
4) ability to photosynthesis
5) ability to fix nitrogen from the atmosphere (even if there is soil it will have little or no nutrients)
6) tolerance to extreme conditions

88
Q

What common features emerge during any succession?

A

1) the abiotic environment becomes less hostile
2) there is a greater number and variety of habitats and niches
3) increased biodiversity
4) more complex food webs
5) increased biomass

89
Q

Describe how biodiversity changes during succession?

A
  • increases in the early stages
  • peaks mid succession
  • decreases as climax community is reached (due to dominating species out-competing pioneer and other species which leads to them being eliminated from the community)
90
Q

What is the climax community of a secondary succession like?

A

because the land has been altered in some way, some of the species in the climax community will be different

91
Q

When is there the most biomass in succession?

A

mid-succession

92
Q

Define conservation

A

the protection and management of ecosystems in a sustainable way

93
Q

Define plagioxlimax

A

the name of the climax community when succession is stopped artificially (ie. regularly mowing the lawn prevents succession)

94
Q

Why do we sometimes prevent succession?

A

to preserve an ecosystem in its current stage of succession.

Eg. areas of moorland in Scotland provide habitats for many species of plants and animals. If succession were left to naturally occur it would lead to a climax community of a spruce forest which would mean loss of the moorland habitat and species that currently live there.

95
Q

How can we manage succession in order to conserve an ecosystem? (2)

A

1) animals grazing on land - animals eat growing points of shrubs and trees, stopping them from establishing themselves and keeping vegetation low
2) managed fires - after fires, secondary succession occurs on the moorland; pioneer species grow back and are conserved whereas larger species take longer to grow back and are removed again in the next fire.

This all prevents climax community being reached

96
Q

What does conservation aim to maintain?

A

ecosystems & biodiversity

97
Q

What are the main reasons for conservation? (4)

A

1) personal - maintain our planet and life support system
2) ethical - other species have occupied earth long than us and should be allowed to coexist with us. Respect for living things.
3) economic - living organisms contain a huge pool of genes that have the capacity to make millions of substances and could be valuable in the future. Long term productivity greater if ecosystems are maintained.
4) cultural and aesthetic - habitats and organisms enrich our lives, add variety and interest to life.

98
Q

What is there conflict between when it comes to conservation?

A

human needs and conservation

  • a balance must be found between the two to ensure natural resources can be sustained
99
Q

Explain the Maasai Mara national reserve in Kenya example

A
  • it’s a grassland with lots of wildlife
  • Maasai people earn a living by raising livestock however this conflicts with conservationalists as livestock and overgrazing can destroy the grassland and wildlife
  • Conservation trusts work with the people to help them make money through ecotourism and conservation, farming in a sustainable way.
  • so economic needs are met whilst wildlife is conserved
100
Q

What are 4 methods of conservation?

A

1) plants conserved with seedbanks (stores seeds from plant species that can be planted if plant becomes extinct)
2) Fishing quotas - limits amount of certain fish species that can be fished and killed.
3) Protected areas - national parks and nature reserves protects habitats and species within them. Restricts urban and industrial development, farming.
4) endangered species bred in captivity then returned to the wild

101
Q

Explain why most of the sun’s energy is not converted into organic matter by photosynthesis (4)

A

1) over 90% of the sun’s energy is reflected back into space by clouds and and dust
2) not all wavelengths of light can be absorbed and used for photosynthesis
3) light may not fall on a chlorophyll molecule
4) other factors might be limiting photosynthesis (eg. CO2 availability)

102
Q

Define Gross Primary Production (GPP)

A

the total quantity of the chemical energy store in a plants biomass in a given area or volume at a given time

103
Q

What percentage of their GPP do plants use in respiration?

A

20-50% of the GPP used for respiration

104
Q

Define Net Primary Production (NPP) and give the equation.

A

quantity of chemical energy store left after respiratory losses to the environment are taken into account

NPP = GPP - R

105
Q

State the equation linking R (respiratory losses), NPP and GPP.

A

NPP = GPP - R

Net Primary Production = Gross Primary Production - Respiratory Losses

106
Q

What is net primary production available for?

A

Plant growth and reproduction

107
Q

When primary consumers eat plants, how much of the plants’ NPP are they usually able to use for their own growth?

A

10%

108
Q

When secondary and tertiary consumers eat their prey, how much of the prey’s NPP are they able to use for their own growth?

A

20%

109
Q

What are reasons for the low transfer of energy at each trophic level?

A

1) some parts of the organism not consumed
2) some parts not digested so are lost in faeces
3) some energy lost in excretory material (eg. urine)
4) energy loss occurs as heat from respiration (losses are high in mammals and birds due to high body temperatures. Much energy is needed to maintain their body temperature when so much heat is constantly lost )

110
Q

How is the net production of consumers calculated?

A

N = I - (F + R)

N = net production
I = chemical energy store of ingested food
F = energy lost in faeces and urine
R = energy lost in respiration
111
Q

What does inefficiency of energy transfer between trophic levels cause (3 things)

A

1) food chains to only have 4 or 5 trophic levels because insufficient energy is available to support a large enough breeding population at trophic levels higher than this.
2) the total mass of organisms (biomass) in a particular place is LESS at higher trophic levels.
3) the total amount of energy available at each trophic level is less as you move up a food chain/trophic level.

112
Q

Define biomass

A

total mass of living material in a specific area at a specific time

113
Q

How can biomass be measured?

A

mass of carbon/ dry mass of tissue
per area
in a given time

114
Q

Disadvantage of measuring biomass as dry mass?

A

because the organism must be killed it is usually only a small sample which may not be representative of the biomass of the whole organism.

115
Q

What are the units of biomass when an area is being sampled?

A

g/m^2

116
Q

What are the units of biomass when a volume is being sampled?

A

g/m^3

117
Q

What does calorimetry measure?

A

the chemical energy store in dry biomass

118
Q

Explain how bomb calorimetry works.

A
  • a sample of dry material weighed
  • sample burnt in pure oxygen
  • in sealed container called a ‘bomb’
  • ‘bomb’ surrounded by water bath
  • heat from combustion raises temperature of the water

energy released from mass of burnt biomass - Q = mc delta t

119
Q

energy units?

A

J/g

KJ/Kg

120
Q

What do plants use sunlight for?

A

making organic products from carbon dioxide and water (these include sugars which are used as respiratory substrates). Other organic products are other biological molecules which form the biomass.

121
Q

Producers

A
  • photosynthetic organisms

- manufacture organic substances from light, water, carbon dioxide and mineral ions

122
Q

Consumers

A

organisms that obtain energy by feeding on other organisms rather than using energy from sunlight directly

123
Q

secondary or tertiary consumers are usually predators however sometimes they are considered as…

A

scavengers or parasites

124
Q

Saprobionts (decomposers)

A
  • break down complex materials in dead organisms into simpler materials, releasing valuable minerals and elements which can be absorbed by plants
125
Q

Example of saprobionts

A

fungi and bacteria

126
Q

Food chain

A

describes a feeding relationship

127
Q

Food webs

A

interlinked food chains within a single habitat

128
Q

What do the arrows represent on a food chain?

A

direction of energy flow

129
Q

What is each stage of a food chain called?

A

a trophic level

130
Q

Why is biomass sometimes hard to calculate?

A

varying amounts of water within the biomass

131
Q

Limits of food chains

A

-don’t reflect the complex feeding relationships in an ecosystem and give the false impression that each organisms only eats one other thing

132
Q

How do we measure the mass of dry mass?

A
  • sample of organism dried in an oven
  • sample weighed at regular intervals
  • when mass becomes constant all the water has been removed
133
Q

Estimate for mass of carbon present in dry mass

A

50% of dry mass

134
Q

Net primary production is…

A

AVAILABLE TO OTHER TROPHIC LEVELS IN THE ECOSYSTEM SUCH AS HERBIVORES AND DECOMPOSERS

135
Q

Define primary productivity

A

rate at which plants and other photosynthetic organisms produce organic compounds in an ecosystem

136
Q

Define primary/secondary productivity (kerboodle)

A

rate of primary/secondary production

137
Q

Typical units of primary/secondary productivity

A

kJ/ha/year (kilo-joules per hectare per year)

138
Q

Typical units of primary/secondary productivity

A

kJ/ha/year (kilo-joules per hectare per year)
OR
kJ/m^2/year

139
Q

What is net production?

A

chemical energy left in the consumer that is now stored in its biomass (after losses through faeces and respiration)

AQA A level Biology (36 decks)

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