7C - Populations in Ecosystems

Question 1

What is a ‘habitat’?

Answer 1

• place where an organism lives

Question 2

What is a ‘population’?

Answer 2

• all the organisms of one species in a habitat

Question 3

What is a ‘community’?

Answer 3

• populations of different species in a habitat

Question 4

What is an ‘ecosystem’?

Answer 4

• a community plus all the non-living (abiotic) conditions in the area in which it lives

Question 5

What are abiotic conditions?

Answer 5

• non-living features of ecosystem e.g temperature and water availability

Question 6

What are biotic conditions?

Answer 6

• living features of ecosystem e.g predators

Question 7

What is a ‘niche’?

Answer 7

• role of a species within its habitat e.g. what it eats, where and when if feeds

Question 8

What is meant by an ‘adaptation’?

Answer 8

• a feature that members of a species have that increases chance of survival and reproduction

Question 9

How many species can occupy one niche?

Answer 9

• one

Question 10

What happens if two species try to occupy a niche?

Answer 10

• they will compete with each other until only one is left

Question 11

Which two conditions do organisms need to adapt to?

Answer 11

• biotic and abiotic

Question 12

What are the three types of adaptations?

Answer 12

• structural
• behavioural
• physiological

Question 13

3 examples of abiotic adaptations

Answer 13

• Otters having webbed paws to swim
• Seals having a thick layer of blubber to keep them warm
• Hedgehogs hibernating to conserve energy

Question 14

3 examples of biotic adaptations

Answer 14

• Sea otters use rocks to smash open shellfish
• Male frogs use mating calls to attract females of the same species
• Bacteria produce antibiotics to kill other bacteria to remove competition

Question 15

What can affect population size abiotically?

Answer 15

• The abiotic conditions can limit how large a population can grow such as food and water availability

Question 16

What are the three biotic factors affecting population size?

Answer 16

• Intraspecific competition
• Interspecific competition
• Predation

Question 17

How does intraspecific competition affect population size?

Answer 17

• If two species compete within the same niche, resources are limited
• meaning both population sizes are more limited until the better adapted species outperforms the other and survives

Question 18

How does interspecific competition affect population?

Answer 18

• If there aren’t many organisms of a species in a habitat they have lots of resources so are able to reproduce but they reproduce too much so now there are too many organisms so the number of organism fluctuates above and below the carrying capacity

Question 19

How does predation affect population size?

Answer 19

• As prey population increases there is more food for predators so that population increases
• However as predator population increases then more prey is eaten but then there isn’t enough food so predator population falls

Question 20

What is the carrying capacity?

Answer 20

• The maximum stable population size that an ecosystem can support

Question 21

Why the predator-prey more complicated that conveyed in the predation idea?

Answer 21

• Predation isn’t the only thing that reduces prey population size

Question 22

How do you generally take a random sample?

Answer 22

• Choose an area to sample
• Use a random number generator to generate coordinates within the area
• Use an appropriate technique to take a sample
• Repeat this process and calculate an average and multiply it by the size of the area

Question 23

What are the two non-motile methods of sampling?

Answer 23

• quadrats

- transects

Question 24

Describe how quadrats can be used to sample.

Answer 24

• A quadrat is a square frame split into 100 squares by strings, you place it at different points in the area and the species frequency is how often a species is found in each quadrant
• You can also calculate percentage coverage in the quadrat by the number of squares which have more than half covered

Question 25

How can transects be used for sampling?

Answer 25

• If you use transects to see how things are distributed across an area, you put a transect across an area
• belt transect with quadrats placed all along the transect
• or a interrupted belt transect where there are quadrats places at intervals along the transect

Question 26

What is the method for sampling motile species?

Answer 26

• mark-release-recapture

Question 27

Describe how to carry out a Mark-Release-Recapture investigation

Answer 27

• Capture a sample using a appropriate technique such as a trap
• Mark then in a harmless way
• Release them into the habitat
• Wait a week and take a second sample
• Count how many of the second sample are marked and you can figure out the population size from pop = (1st sample size x 2nd sample size)/number marked in 2nd sample

Question 28

What assumptions are made in the Mark-Release-Recapture method?

Answer 28

• The sample has enough time and opportunity to mix back in with the population
• The marking hasn’t affected the chance of survival and its still visible
• There are no changes in population size due to birth death migration etc

Question 29

What is succession?

Answer 29

• the process by which an ecosystem changes over time

Question 30

What are the two types of succession?

Answer 30

• primary and secondary

Question 31

What is primary succession?

Answer 31

• succession that occurs on surfaces where no soil exists

Question 32

What is secondary succession?

Answer 32

• Succession following a disturbance that destroys a community without destroying the soil

Question 33

Describe what happens during primary succession.

Answer 33

• Seeds and spores (pioneer species) blow on to the land and begin to grow, abiotic conditions are harsh so only pioneer species can grow
• once these die they decompose and add to the basic soil making the conditions less hostile so more species can grow which die and add further to the soil
• newer species can actually change the environment so that other species can’t grow anymore

Question 34

Describe how secondary succession occurs.

Answer 34

• Secondary succession starts with soil so the pioneer species are larger plants
• becomes more and more complex with species competing to become dominant as biodiversity increase
• most complex community is called the climax community which won’t change much

Question 35

How do climax communities vary for different ecosystems?

Answer 35

• The climax community for a particular climate is called the climatic climax e.g. in a temperature climate there’s more water available and milder temperatures so larger trees can exist however in polar climates there’s not much water available, low temperatures and extreme climate so the climatic climax only contains herbs or shrubs

Question 36

What is a plagioclimax?

Answer 36

• When succession is stopped artificially

Question 37

How does conservation involve managing succession?

Answer 37

• Often some climax communities involve larger forest which get rid of marshlands etc which are the habitat of many species so conservation can involve mowing the grass so no trees grow or allowing cows to graze there so no trees grow

Question 38

What is conservation?

Answer 38

• The protection and management of an ecosystem

Question 39

What conflicts can be had between conservation and human needs?

Answer 39

• Some farming is quite aggressive and leaves the land bare but it is some people’s way of life and human business demand requires a large income of resources

Question 40

How can business be made better for conservation?

Answer 40

• Teach sustainable farming
• Plants conserved in seed banks
• Fishing quotas added
• Protected areas such as national parks
• Endangered species bred in captivity to increase numbers