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Y13 Biology > Topic 7 C: Populations in Ecosystems > Flashcards

Topic 7 C: Populations in Ecosystems Flashcards

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1
Q

What is an ecosystem?

A

All the organisms living in a community and all the non-living factors of its environment.

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2
Q

What is ecology?

A

Study of the inter-relationships between organisms and their environments.

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3
Q

Biotic definitions?

A

Living things that affect an organisms e.g., competition

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4
Q

Abiotic definitions?

A

Non-living things that affect an organisms e.g., temperature

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5
Q

Examples of biotic factors?

A
  • pathogen spread through population
  • arrival of a competitor species
  • parasites
  • increase in number of predators
  • arrival of a new supply of food source
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6
Q

Examples of abiotic factors?

A
  • rise in temperature
  • a drop in rainfall
  • change in the light intensity
  • rise in co2 levels
  • change in water ph
  • change in wind intensity/direction
  • lower levels of nutrients in soil
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7
Q

Biosphere definition?

A

All parts of the earth where life exists (all ecosystems)

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8
Q

Biome definition?

A

Climate / geographic defined areas of ecologically similar communities of plants and animals.

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9
Q

Community definition?

A

Populations of different species living in the same environment / habitat (often named after dominant plant as they are rooted in place and are easy to find/see whereas animals roam between communities)

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10
Q

Population definition?

A

All the individuals of one species living together in the same place at the same time.

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11
Q

Individual definition?

A

Single member of a species.

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12
Q

Why is ecosystem interdependent?

A

All organisms rely on eachother and the environment to survive.

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13
Q

Two major processes to consider in ecosystem?

A
  • flow of energy through system
  • cycling of elements within system
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14
Q

Habitat definition?

A

Area where one or more organisms live (abiotic).

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15
Q

Microhabitat definition?

A

Within each habitat there are smaller units.

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16
Q

Carrying capacity definition?

A

Maximum number of individuals in a species that an environment can support for the long term.

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17
Q

Limiting factors for carrying capacity?

A

Food, water, shelter, space, disease, predation, and climatic conditions.

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18
Q

What does the carrying capacity graph look like?

A

S shaped - then declined.

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19
Q

Niche definition?

A

Particular roles that an organism plays within the community / ecosystem - where it lives and what it does.

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20
Q

What does the ecological niche depend on?

A
  • range of abitotic factors it can tolerate
  • the resources in the ecosystem that its able to make use of (e.g., soil nutrients available, oxygen levels, prey etc)
  • its interactions with other organisms (biotic)
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21
Q

Difference between interspecific and intraspecific competition?

A
  • interspecific = between two or more different species
  • intraspecific = within same species
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21
Q

What happens in ecosystems with overlapping niches?

A
  • competition will occur as they will all try to use the same resources which are short in supply
  • the more similar the individuals are, the more intense the competition
  • not possible for two species to have the exact same niches, they would outcompete.
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22
Q

Which type is more intense and why?

A

Intraspecific competition more intense because individuals have same niches so compete for the exact same things - individuals that are better competitors will have greater chance of surviving to reproduce and pass on genes.

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23
Q

How do bacteria reproduce?

A

Asexually through binary fission to track its exponential growth.

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24
Q

What is the lag phase?

A

Slow increase in the number of microbes as they have to acclimate to environment and start off with one.

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25
Q

What is log phase?

A

Rapid increase as more cells are undergoing binary fission - exponential growth.
- birth rates exceed death rates due to the abundance of resources e.g., oxygen and nutrients

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26
Q

What is stationary phase?

A

Maximum carrying capacity is reached and resources such as food and water are limiting
- birth rates = death rates

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27
Q

What is death phase?

A

Number of bacteria decrease as not enough resources so they compete for resources, individuals that are better competitors survive and reproduce
- death rates exceed birth rates

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28
Q

Limiting factors on bacterial growth?

A

abiotic = nutrient levels, accumulation of metabolic waste, and oxygen levels
biotic = competition and new bacteria introduced (contamination)

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29
Q

What scale is used to measure bacteria population size and why?

A

Logarithmic scale due to extremely high population levels

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30
Q

How to use log on calculator?

A

Press shift then log.

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31
Q

Exam question: identify how mineral ions being the limiting factor would control the bacterial population size?

A
  • mineral ions are consumed as the population becomes larger
  • the population becomes so large that the bacteria at the surface prevent light reaching those at deeper levels
  • other species are introduced into the pond, carried by animals or the wind, and some of these species may use the bacteria as food or compete for light or minerals
  • winter brings much lower temperatures and lower light intensity of shorter duration
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32
Q

How does temperature affect the carrying capacity of the population?

A
  • each species has a different optimum temperature at which enzymes work best. low temperatures below optimum = enzyme activity slower = metabolic rate reduced = decreased growth rate.
  • high temp = denature
  • warm blooded animals maintain constant body temp (homeostasis) despite changing external conditions, however their carrying capacity still affected by temperature as energy used in maintaining normal body temp = less energy for growth
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32
Q

How does light affect carrying capacity?

A
  • source of energy in ecosystem. rate of photosynthesis increases with increased light intensity = faster growth rate and more seed/spore production (reproduction).
  • in turn, animals have larger carrying capacity as more able to feed
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32
Q

How does pH affect carrying capacity?

A
  • pH affects rate of enzyme activity - deviating from optimum pH leads to decline in population size as conditions not ideal for growth
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33
Q

How does water and humidity affect carrying capacity?

A
  • humidity levels affect transpiration rate in plants and evaporation of water from animals’ bodies.
  • only populations adapted to dry, low humidity conditions would have a larger carrying capacity
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34
Q

Example of intraspecific competition?

A
  • oak trees compete for resources, some will grow larger and restrict light availability, water, and minerals.
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35
Q

Example of interspecific competition?

A
  • red and grey squirrels, grey outcompete because larger sa:v ratio (so store more fat for heat in winter), colour allows them to camouflage, large tail maintains their stability when climbing trees, squirrel pox virus harmful to red but not grey.
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36
Q

What is the competitive exclusion principle?

A

Where two species are competing for limited resources, the one that uses these resources most effectively will eliminate the other.

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37
Q

How to consider if a factor affects population size?

A

Refer to birth and death rates.

38
Q

Model Answer: Discuss whether it would be possible for two species living in the same habitat to possess the same niche?

A
  • niche = specific role an organism plays in community
  • e.g., food it eats, where it lives, and how it interacts with abiotic and biotic factors
  • for two species to exist indefinitely in a habitat, niches cant overlap
  • overlap in niches cause interspecific competition
  • species with feature which give competitive advantage use resources more effectively and eliminate competitor species
  • competitive exclusion principle
39
Q

Predation definition?

A

When one species of animal, the prey, is caught and eaten by another, the predator.

40
Q

Describe the pattern of predator-prey graphs?

A

Cyclic fluctuation

41
Q

Describe predator-prey graph cycle?

A
  • predator eats prey, prey pop decreases
  • few prey available so predation in greater competition
  • predator population decrease as some are unable to obtain enough prey for survival
  • few predators left, fewer prey eaten so more survive and reproduce
  • prey pop increase
  • more prey available = predator pop increases
42
Q

Why are studies on populations of animals in predator-prey relationships difficult to carry out?

A
  • predators may have more than one prey so cycles may not show distinct changes
  • other factors such as climate, disease etc could affect population size
43
Q

Significance of the lowest points (troughs) in predator-prey graphs?

A
  • predator/prey pop fall very low due to lack of food or increased predation - selection pressures
  • vital for ‘rooting out’ the ‘fittest’ members of a species that can survive and reproduce under these pressures - drives evolution
44
Q

Exam question: Explain why a predator population exterminates prey population in lab but not natural habitat?

A

The range and variety of lab habitats much smaller than natural ones. in nature there is a greater range of hiding spaces so prey have more space and places to escape predator and survive.

45
Q

Exam question: explain how a fall in the population of a predator can lead to a rise in its prey population?

A

Fewer predators mean fewer prey taken as food. the death rates of prey reduced, assuming the birth rate remains unchanged, the population size increases.

46
Q

Succession definition?

A

Describes changes to the species present in a community over time due to changes in environment/abiotic factors

47
Q

Succession stages?

A

bare rock - colonised by pioneer species e.g., moss - decomposition creates layer of topsoil - grasses grow and displace pioneer species - more nutrients in soil allow for shrub growth - increase in soil depth allows for growth of large trees (climax community)

48
Q

Stage one - bare rock?

A
  • rock impenetrable by roots
  • no nutrients in soil
  • no primary/secondary consumers
  • extreme microclimate, as the bare ground absorbs and reflects heat
  • dry = no plant cover to hold moisture
49
Q

Stage two - pioneer species?

A
  • colonise bare rock
  • adapted to extreme, less ideal conditions (extremophiles)
  • asexually reproduce = rapidly multiply population
  • rapid seed germination
  • photosynthetic so dont rely on other organisms for food
  • fix nitrogen from atmosphere, providing nutrient to environment
  • grow in cracks to avoid wind
50
Q

Before and after pioneer species?

A
  1. B = rock impenetrable by roots. A = lichen and moss penetrate rock, breaking it into smaller pieces
  2. B = no nutrients. A = pioneer species die, and add nutrients to the soil through decomposition and nitrogen fixation when alive
  3. B = no secondary consumers. A = as pioneer species grow, they provide food and habitats for animals.
  4. B = extreme microclimate. A = soil becomes more nutrient-rich and habitat less extreme/hostile so different animal and plant species can live there
  5. B = dry. A = humus (dead matter) added to soil which increases water retention allowing more species to live there
51
Q

Stage four, five and six of succession?

A

4 - larger plants that need more water move in soil as it deepens e.g. grass and small flowering plants. soil continues to deepen as plants die and decompose
5 - shrubs, ferns, and small trees grow, outcompeting grasses and smaller plants to become the dominant species, diversity increases
6 - soil deep and rich enough in nutrients to support large trees, they become the dominant species and the climax community.

52
Q

Climax community definition?

A

The stable community that is reached where no further succession occurs, and environments carrying capacity is reached. (stable equilibrium)

53
Q

Features of climax community?

A
  • population size stable
  • same species present
  • abiotic factors are more or less constant
54
Q

Exam question: what drives succession (1)?

A

Changes in environment.

55
Q

Exam question: How does the presence of the pioneer species allow succession to occur?

A
  • when die and decompose they release nutrients into soil due to nitrogen fixation and photosynthesis when alive to produce food e.g, glucose
  • make habitats less hostile so more species can live there
  • produce humus which increases water retention of soil
  • environment more suited to new species who are able to adapt due to competitive advantage, current species less adapted in new conditions.
56
Q

Where does primary succession occur?

A

Land that has been newly formed or exposed

57
Q

Where does secondary succession occur?

A

Land that has been cleared of all the plants but soil remains
(e.g., forest fires, war, harsh weather conditions, volcanic eruption, deforestation, building farms, mowing)

58
Q

Which type of succession is faster and why?

A

Secondary because soil is already there, so dont need the first couple of stages of primary succession such as having a pioneer species.
- also animals can migrate rapidly to these areas

59
Q

Example of secondary succession?

A
  1. stable forest community
  2. disturbance e.g., wild fire
  3. fire burns forest
  4. leaves behind empty but not destroyed soil
  5. grass and other herbaceous plants grow first
  6. small bushes and trees colonise area
  7. fast growing trees develop
  8. short-lived and shade intolerant trees die as large ones overtop them and gain most sunlight, ecosystem now back ti similiar state as it began
60
Q

Abundance and distribution definition?

A

Abundance = number of individuals of one species in a particular area (num of each species)
Distribution = where a particular species is within the area you’re investigating (how they are spread out)

61
Q

Abundance frequency and percentage cover?

A

Frequency = number of samples a species is recorded in
Percentage cover = how much of an area is covered by a species

62
Q

Validity, accuracy, and precision definition?

A

Validity = control variables have been controlled so no other factors affect results
Accuracy = close to true value
Precision = repeat to get the same outcome, might not necessarily be accurate

63
Q

Random sampling pro and con?

A
  • eliminate bias = pro
  • less reliable = con
64
Q

Random sampling process? (investigatng effect of grazing on plant species)

A
  1. find two different fields, one grazed one not. Ensure the fields are close together to minimise soil, climate and other abiotic differences
  2. lay out tape measure at right angle to create axis along the sides of the field, then use random number generator to select coordinates for sampling. place quadrats at coordinates
  3. count number of organisms in quadrats and record the name of each species
  4. repeat process by taking further samples at different coordinates and calculate a mean. then multiply the mean number of organisms by area of field
65
Q

Systematic sampling pro and con?

A
  • more reliable = pro
  • time consuming = con
66
Q

How systematic sampling compares to random?

A
  • samples taken at regular intervals instead of random
67
Q

Types of quadrats?

A
  1. frame = square frame divided into smaller squares
  2. point = horizontal bar supported by two legs, at set intervals along the bar there are 10 holes where pins can be dropped. species that touch the pin are counted
68
Q

Considerations when using quadrats?

A
  1. size - depends on size of species
  2. number - more is more reliable
  3. position - random or systematic?
69
Q

Types of transects?

A
  1. belt transect = quadrats are placed next to eachother along the transect to work out species frequency and percentage cover along the transect.
  2. interrupted belt transect = instead of investigating whole transect, you can take measurements using a quadrat placed at regular intervals
70
Q

Exam question: What is the aim of random sampling and how is it achieved in ecological studies?

A
  • eliminate bias
  • after creating an axes and grids, use a random number generator for coordinates
71
Q

Exam question: What is systematic sampling and why/when would this be used?

A
  • sample taken at regular intervals to get more reliable results
  • used when trying to track the effect of a changing independent variable
72
Q

Abundance definition?

A

Number of individuals of a species within a given area

73
Q

Density definition, how does it work, advantages and disadvantages?

A

-actual number of individuals of one species in an area
- count number of individuals of one species in one quadrat x by the area of whole field
- more accurate to count each one
- more time consuming and not reliable as could count incorrectly

74
Q

Frequency definition, how does it work, advantages and disadvantages?

A

-likelihood of / how often a particular species is present in a quadrat (how many boxes)
- count the number of boxes within the quadrat that the species are in
- fast and covers a large area, can be used for plant species that are hard to count individually e.g., grass
- not very accurate, size of plant not considered or plants that overlap

75
Q

Percentage cover definition, how does it work, advantages and disadvantages?

A

-estimate for the area within a quadrat that a particular plant species covers
- same as definition
- fast and useful for species where individuals are hard to count
- not very accurate as it is subjective, plant size not considered or plants that overlap

76
Q

Mark release recapture method?

A
  1. known number of species is captured and marked/tagged, without reducing their chances of survival
  2. marked organisms released
  3. enough time allowed for individuals to disperse through population
  4. another known number of organisms are captured
  5. number of these that are marked are recorded
77
Q

mark release recapture formula?

A

total population size =
num caught in 1st sample x num caught in 2nd sample / number marked in 2nd sample

78
Q

What assumptions does mark release recapture rely on?

A
  • proportion of marked to unmarked in 2nd sample = proportion of marked to unmarked in whole population
  • first sample distributes evenly with population
  • no immigration / emigration
79
Q

Types of nets used to trap certain animals?

A
  1. flying insects = sweep net
  2. aquatic animals = net
  3. ground insects = pitfall trap
80
Q

Exam question: When using the mark release recapture technique, explain how each of the following might affect the final estimate of a population?
The marks put on the individuals captured in 1st sample make them more easily seen by predators and so proportionately more are eaten than the unmarked.

A

Overestimate as there are proportionately fewer marked individuals in the 2nd sample

81
Q

Exam question: When using the mark release recapture technique, explain how each of the following might affect the final estimate of a population?
Between the release of marked individuals and the collection of a second sample an increased birth rate leads to a very large increase in the population.

A

Overestimate as there will be proportionately fewer marked individuals in the second sample because all the ‘new’ individuals will be unmarked

82
Q

Exam question: When using the mark release recapture technique, explain how each of the following might affect the final estimate of a population?
Between the release of marked individuals and the collection of a second sample, disease kills large numbers of all types of individual.

A

No difference because the proportion of marked and unmarked individuals killed should be the same

83
Q

Major issue in todays society?

A

Exctinction - sixth event = Holocene Extinction Event.
- Extinction has always been an ongoing feature of life on Earth, and is a natural consequence of evolution.​
- Since life began, there have been at least five mass extinction events – a sharp decrease in the number of species in a relatively short period of time.

84
Q

Some consequences of potential extinction?

A
  • threat to food supply
  • declined biodiversity
  • bee populations could collapse
  • increased acidity of oceans kill coral reef
85
Q

How humans are decreasing biodiversity?

A
  • habitat destruction – e.g. deforestation for urban development and agricultural land, global warming, mining and pollution​
  • overexploitation – e.g. whaling, fishing and wildlife trade
  • competition from introduced species – e.g. grey vs. red squirrels in the UK
  • usage of greenhouse gases
86
Q

Conservation definition?

A

Management of the earths natural resources by humans in such a way that maximum use of them can be made in the future

87
Q

5 reasons for conservation?

A
  1. personal
  2. economical
  3. ecological
  4. ethical
  5. cultural
88
Q

Personal reasons for conservation?

A
  • To main our planet and our life support systems.
  • veganism / vegetarianism
89
Q

Economical reasons for conservation?

A
  • Zoos, safari parks and other conservation sites attract tourists
  • Products and substances can be produced by living organisms and sold – e.g. drugs, oils etc.
90
Q

Ecological reasons for conservation?

A
  • Help to regulate atmosphere
  • Form and fertilise the soil
  • Help with crop pollination
  • Purify and retain water
  • Produce food material
91
Q

Cultural reasons for conservation?

A
  • Acts as an inspiration for authors, poets, composers, artists etc.
92
Q

Ethical reasons for conservation?

A
  • all species have a right to exist and there is an ethical reason to ensure they survive
  • Humans, as the dominant species on Earth and a major cause of the current reduction in biodiversity, should be responsible for the protection of the natural environment
  • Should be preserved for the benefit and enjoyment of future generations.
93
Q

Methods in place to conserve plants and animals?

A
  • Managing and protecting species in their natural habitats (in-situ) = enhancing shelter and food sources, reducing predation etc.​
  • Coppicing/Cutting down trees to ground level to promote re-growth – longevity of trees increased and microhabitats produced.​
  • Removing organisms from habitats (ex-situ) as their habitats have become unsuitable for their survival.​
  • Captive breeding programmes in zoos – increases number of endangered species that can be reintroduced into the wild. ​
  • Seed banks – storing seeds of plants from different species so they can be regrown if they for (maintain genetic diversity). Temperature controlled environments required. ​
  • Studying habitats and species to have a better understanding of them and how they can be managed – educating people about conservation.​
94
Q

How is conservation linked to succession?

A
  • Communities undergo a series of successional changes to reach their final Climate Community.​
  • Many of the species that existed in the earlier stages are no longer present due to the disappearance of or changes to their habitat as a result of succession, or species have been out-competed by other species, or taken over for human activity.​
  • In terms of conservation, stopping a community from reaching its climax community may be beneficial!​
  • The species in the earlier stages are more diverse and provide food and resources for a higher diversity of animal species to exist.
95
Q

Methods of inhibiting succession?

A
  • e.g. UK moorland ​= Controlled burning of shrubs and trees allows the growth of heather in moorland and grazing by sheep has prevented this land from reaching its climate community.

Y13 Biology (11 decks)

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