Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology > 19. Populations in ecosystems > Flashcards

19. Populations in ecosystems Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is ecology?

A

Ecology is the study of inter-relationships between organisms and their environment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Give examples of abiotic factors

A
  • Temperature

- Rainfall

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Give examples of biotic factors

A
  • Competition

- Predation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is an ecosystem?

A

Ecosystems are dynamic systems made up of a community and all the abiotic factors of its environment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the 2 major components to consider in an ecosystem?

A
  • The flow of energy through the system

- The cycling of elements within system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a population?

A

A population is a group of i divisors of one species that occupy the same habitat at the same time and are potentially able to interbreed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Define ‘carrying capacity’

A

A certain size of a population a species can support.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What factors vary the size of the population?

A
  • The effect of abiotic factors

- Interactions between organisms (e.g. intraspecific & interspecific competition)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is a community?

A

All the populations of different species living and interacting in a particular place at the same time.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is a habitat?

A

A habitat is the place where an organism normally lives and is characterised by physical conditions and the other types of organism present.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is an ‘ecological niche’?

A

A niche describes how an organism fits into its environment. It describes what a species is like, where it occurs, how it behaves, its interactions with other species and how it responds to its environment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Bacterial growth is very fast, how is its rate measured?

A

Using a logarithmic scale.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What factors slow/cease the growth of bacterial population (with optimum conditions so no limiting factors)

A
  • Mineral ions are consumed so the population becomes larger
  • The population becomes large so 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 air of these species may use the bacteria as food/compete for light
  • Winter brings much lower temperatures and lower light intensity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Give examples of abiotic factors that influence population size

A
  • Temperature
  • Light
  • pH
  • Water/humidity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why does temperature affect population size in plants & cold blooded animals?

A

Each species have different optimum temperatures; as temps fall below optimum, enzymes work it’s slowly and so metabolism is reduced. Populations therefore have a smaller carrying capacity. At temps above optimum enzymes undergo denaturation so work less efficiently. Again, reduces carrying capacity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why does temperature affect population size in warm blooded animals?

A

The further the temperature of the external environment gets from their optimum temperature, the more energy the organism expends in trying to maintain their normal body temperature. This leaves less energy for individual growth and so they mature more slowly and their reproductive rate slows. Carrying capacity is reduced.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why does light affect the population size?

A

As the ultimate source of energy for most ecosystems, the rate of photosynthesis increases as light intensity increases. The greater the rate of photosynthesis, the faster plants cos and the more spores or seeds they produce. Their carrying capacity is therefore greater. In turn the carrying capacity of animals that feed on plants is larger.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Why does pH affect population size?

A

Each enzyme has an optimum pH at which it operates most effectively. A population of organisms is larger where the appropriate pH exists and smaller where the pH is different from the optimum.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Why does water/humidity affect population size?

A

Where water is scarce, populations are small and consist only of species that are well adapted to living in dry conditions. Humidity affects the transpiration rates in plants and the evaporation of water form the bodies of animals.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Explain why populations never grow indefinitely

A

Certain factors limit growth- e.g. accumulation of waste, availability of food, disease.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Distinguish between biotic and abiotic factors

A

Biotic factors involve the activities of living organisms.

Abiotic factors involve the non-living part of the environment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Suggest the level and type of abiotic factor that is most likely to limit the population size of ground plants on forest floor.

A

Low light intensity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Suggest the level and type of abiotic factor that is most likely to limit the population size of hares in a sandy desert

A

Lack of water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Suggest the level and type of abiotic factor that is most likely to limit the population size of bacteria on the summit of a high mountain

A

Low temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What do animals compete for?

A
  • Food
  • Water
  • Territory
  • Shelter
  • Mates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What do plants compete for?

A
  • Light
  • Water
  • Minerals
  • Space
  • Carbon dioxide
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is competition?

A

When 2 or more individuals share any resource (e.g. light, food, space) that is insufficient to satisfy all of their requirements fully. Often organisms that are more similar, and have the same niche, have the most competition.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is intraspecific competition?

A

Intraspecific competition occurs when individuals of the same species compete with one another for resources such as food. It is the availability of such resources that determines the size of a population. The lower the availability, the smaller the population. Availability of resources also affects the degree of competition between organisms, which results in a smaller population.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How does intraspecific competition drive evolution?

A

Individuals best adapted to the pressure will successfully breed and pass on their genes, whilst others die out.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Give examples of intraspecific competition?

A
  • Limpets competing for algae, which is their main food. The more algae available, the larger the limpet population becomes.
  • Oak trees competing for resources. In a large population of small oak trees some will grow larger and restrict the availability of light, water and minerals to the rest, which then die. In time, the population will be reduced to relatively few large, dominant oaks.
31
Q

What is interspecific competition?

A

Occurs when individuals of different species compete for resources such as food, light, water etc. When populations of 2 species are in competition one will normally have a competitive advantage over the other. The population of this species will gradually increase in size, while the population of the other will diminish. If conditions remain the same, this will lead to the complete removal of one species.

32
Q

What is the competitive exclusion principle?

A

This principle states that where 2 species are competing for limited resources, the one that uses these resources will ultimately eliminate the other. No 2 species can occupy the same niche indefinitely when resources are limiting. 2 species of sea birds: shags and cormorants, appear to occupy the same niche, living and nesting on the same cliff and eating fish from the sea. Analysis of their food shows that they feed off different sources, so therefore occupy different niches.

33
Q

Define ‘predator’

A

A predator is an organism that feeds on another organism, known as prey.

34
Q

Give adaptations of predator

A
  • more effective camouflage

- better means of detecting prey

35
Q

Give adaptations of prey

A
  • better camouflage
  • more protective features
  • concealment behaviour
36
Q

Define ‘predation’

A

Predation occurs when one organism is consumed by another.

37
Q

What happens when predator-prey relationships are observed in a lab setting?

A

When populations of both predator and prey are brought together in a laboratory, the prey is usually exterminated by the predator, due to the range/variety of the habitat being confined to a lab.

38
Q

What happens when predator-prey relationships are observed in their natural habitat?

A

In nature, the area over which the population can travel is far greater and the variety of the environment is much more diverse. Organisms eat a range of food so fluctuation in population size is less severe. There are many more potential refuges. Therefore prey can escape predation because the fewer there are the harder they are to find and catch. Therefore, although the prey population falls to a low level, it rarely becomes extinct.

39
Q

Evaluate pros and cons of observation in nature and the lab

A

Evidence collected in laboratories doesn’t always reflect what happens in the wild. However, it is difficult to obtain reliable data from natural populations as it’s impossible to count all the individuals in a natural population. Its size can only be estimated from sampling and surveys, which can’t guarantee accuracy.

40
Q

What is the effect of predator-prey relationship on population size?

A
  • Predators eat their prey, thereby reducing population of prey
  • With fewer prey available the predators are in greater competition with each other for the prey that are left.
  • The predator population is reduced as some individuals are unable to obtain enough prey for their survival or to reproduce.
  • With fewer predators left, fewer prey are eaten and so more survive and are able to reproduce.
  • The prey population increases.
  • With more prey now available as food, the predator population increases.
41
Q

Other than predator-prey relations, what other factors effect population size?

A
  • Disease

- Climate

42
Q

Why are periodic population crashes essential to evolution?

A

There’s a selection pressure which means that those individuals who’re able to escape predator, or withstand disease or an adverse climate, are more likely to survive to reproduce. The population therefore evolves to be better adapted to the prevailing conditions.

43
Q

Explain why a predator population often exterminates a prey population in a laboratory but rarely does so in natural habitats.

A

The range and variety of laboratory habitats is much smaller than natural ones. This means that in nature there’s a greater range of hiding places and so the prey has more space and places to escape the predator and survive.

44
Q

Explain how a fall in the population of a predator can lead to a rise in prey population.

A

With fewer predators, fewer prey are eaten as food. The death rate of prey is reduced. Assuming the birth rate remains unchanged, the population size increases.

45
Q

State 2 different sampling techniques to measure abundance and distribution of species

A
  • Random sampling involves using quadrats

* Systematic sampling along a belt transect

46
Q

What is a point quadrat?

A

A point quadrat consists if a horizontal bar supported by two legs. At set intervals along the horizontal bars are ten holes, though each of which a long pin may be dropped. Each species that the pin touches is then recorded.

47
Q

What is a frame quadrat?

A

A frame quadrat is a square frame divided b string into equally sized subdivisions. It’s often designed so it can be compact for storage/transport. The quadrat is placed in different locations within the area being studied. The level of abundance of each species within the quadrat is recorded.

48
Q

What factors should be considered when sampling with quadrats?

A
  • The size of the quadrat- This will depend on the size of the plants/animals being counted and how they’re distributed throughout the area. Larger species require larger quadrats. Where a population of a species is not evenly distributed throughout the area, a large number of small quadrats will give more representative results than a small number of large ones.
  • The number of sample quadrats to record within the study area- The larger the number of sample quadrats the more reliable the results will be. As the recording of species within a quadrat is a time consuming task, a balance needs to be struck between the reliability of the results and the time available. The greater the number of species present in the area being studied, the greater the number of quadrats required to produce reliable results for a valid conclusion.
  • The position of each quadrat within the study area- random sampling must be used to produce statistically significant results.
49
Q

Give method for random sampling

A
  1. Lay out 2 long tape measures at right angles, along 2 sides of the study area.
  2. Obtain a series of coordinates by using random numbers taken from a table or generated by a computer.
  3. Place a quadrat at the intersection of each pair of coordinates and record the species within it.
50
Q

Why is systematic sampling important?

A

Systematic sampling is particularly important where some form of gradual change in the communities of plants and animals takes place.

51
Q

Describe the process of systematic sampling

A

The stages of succession are shown using transects. A belt transect can be made by stretching a string or tape across the ground in a straight line. A frame quadrat is laid down alongside the line and the species within it recorded. It’s then moved its own length along the line and the process repeated. This gives a record of species in a continuous belt.

52
Q

Define abundance

A

Abundance is the number of individuals of a species within a given area

53
Q

How is abundance measured for organisms that don’t move around?

A
  • Frequency: The likelihood of a species occurring in a quadrat. This method is useful where a species is hard to count, e.g. grass. If a species occurs in 15 of 30 quadrats, the frequency of its occurrence is 50%. It gives a quick idea of the species present and their general distribution within an area. However it doesn’t provide information on the density or the detailed distribution of a species.
  • Percentage cover: An estimate of the area within a quadrat that a particular plant species covers. It’s useful where a species is particularly abundant or hard to count. The advantage is that data can be collected rapidly and individual plants don’t need to be counted. It’s less useful where organisms occur in several overlapping layers (usually plants).
54
Q

Describe the mark-recapture technique

A

Technique used for motile organisms (most animals). A known number of animals are caught, marked, and then released back into the community. Sometime later, a given number of individuals are collected randomly and the number of marked individuals is recorded.

55
Q

How do you calculate population size by the mark-recapture method?

A

total number of individuals from the 1st sample x total number of individuals from the 2nd sample/
number of marked individuals recaptured

56
Q

What assumptions need to be made when using the mark-recapture method

A
  • Proportion of marked to unmarked individuals in the second sample is the same as the proportion of marked to unmarked individuals in the population as a whole.
  • The marked individuals released from the first sample distribute themselves evenly amongst the remainder of the population and have sufficient time to do so.
  • The population has a definite boundary so that there’s no immigration into or emigration out of the population.
  • There’s few, if any, deaths and births within the population.
  • The method of marking is not toxic to the individual or makes the individual more conspicuous and liable to predation.
  • The mark is not lost/rubbed off during the investigation.
57
Q

Why are ecosystems described as ‘dynamic’?

A

Ecosystems change daily as populations fluctuate, slowly or rapidly.

58
Q

Define ‘succession’

A

Succession describes these changes, over time, in the species that occupy a particular area.

59
Q

Give reasons why barren land can arise

A
  • Glacier retreating and depositing rock
  • Piled into dunes by wind or sea
  • Volcano eruption, depositing lava
  • Lakes/ponds created by land subsiding
  • Mud deposited at river estuaries
60
Q

At each stage of succession, a new species colonises the area and may change the environment. How might a species alter the environment?

A
  • Make the environment less suitable for existing species. New species may out-compete old.
  • Make the environment more suitable for other species with different adaptations. Species may be out-competed by better adapted new species.
61
Q

How does succession increase biodiversity?

A

Successional changes alter the abiotic environment, resulting in a less-hostile environment, aiding survival. New communities form, biodiversity increased.

62
Q

What is the ‘pioneer species’?

A

The first organism to colonise an inhospitable environment.

63
Q

What features do pioneer species possess that suit them to colonisation?

A
  • Asexual reproduction- single organism can multiply to grow population.
  • Produce vast quantities of wind-dispersed seeds/spores, reaching isolated situations.
  • Rapid germination of seeds
  • Ability to photosynthesise, light available, food not.
  • Ability to fix nitrogen from atmosphere, soil has no nutrients
  • Tolerance to extreme conditions.
64
Q

What is a climax community?

A

Once the community reaches balanced equilibrium, few new species replacing established species. Many species flourish, much biodiversity. Remains stable over long period of time.

65
Q

What environmental features emerge as a result of succession?

A
  • Less hostile abiotic environment: soil forms, nutrients, plant shelter from wind. Leads to…
  • A greater number and variety of habitats and niches that produce…
  • Increased biodiversity as different species occupy these habitats. Especially evident in early stages, peaking mid-succession, decreasing once climax is reached. Decrease due to dominant species out-competing pioneer, leading to elimination from community. With increased biodiversity comes…
  • More complex food webs leading to…
  • Increased biomass, especially mid-succession.
66
Q

What is secondary succession?

A

Succession occurs when land that already sustained life is altered, e.g. due to land clearance or forest fire. Succession to reach climax is achieved rapidly.

67
Q

Why is secondary succession achieved rapidly?

A
  • Soil exists
  • Spores and seeds alive in soul
  • Influx of plants/animals through dispersion/migration of surrounding area.
68
Q

Describe features of a climax community in a temperate climate

A

Plenty of available water, mild temperatures, little fluctuation between seasons. Climax contains large trees that grow in deep soil.

69
Q

Describe features of a climax community in a polar climate

A

Little available water, low temperatures, massive fluctuation in seasons. Large trees unable to grow in such conditions, so climax contains only shrubs or herbs.

70
Q

Define ‘conservation’

A

Conservation is the management of the Earth’s natural resources by humans in such a way that maximises their future use. Involves active intervention from humans to maintain ecosystems and biodiversity. A dynamic process, entails careful management of existing resources and reclamation of those already damaged by human activities.

71
Q

Give the main reasons for conservation

A
  • Personal to maintain our planet.
  • Ethical: respect to other species that occupy Earth.
  • Economic: living organisms contain a gene pool with the capacity to make millions of substances, valuable in the future. Long-term productivity is greater if ecosystems maintained.
  • Cultural & aesthetic: Habitats enrich life.
72
Q

How does managing succession help conservation?

A

By preventing change to the next stage in succession. Many species present in pioneer community not present in climax community.

73
Q

Give 2 methods of conservation

A
  • Animals allowed to graze on land, eating growing points of shrubs, keeps vegetation low
  • Managed fires lit, after which secondary succession occurs, pioneer species that grow back first are the conserved species. Larger species take longer to regrow.

Biology (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions