Populations in Ecosystems

Question 1

What is a species?

Answer 1

Group of similar organisms which interbreed to produce fertile offspring

Question 2

What is a population?

Answer 2

Group of organisms of the same species living in the same habitat

Question 3

What is a habitat?

Answer 3

The part of an ecosystem where an organism lives

Question 4

What is a community?

Answer 4

All the populations of different species in the same area at the same time

Question 5

What is an ecosystem?

Answer 5

The community of organisms (biotic) and non-living components (abiotic) of an environment
Can be very small to very large

Question 6

What is a niche?

Answer 6

An organisms role within an ecosystem, including their position in the food web + habitat.
No two species can share the same niche otherwise one will be outcompeted (competitive exclusion principle)

Question 7

What is carrying capacity?

Answer 7

The maximum population size an ecosystem can support

Question 8

What are the factors affecting population size?

Answer 8

-Abiotic factors
-Interactions between organisms like interspecific and intraspecific competition + predation

Question 9

What are biotic and abiotic factors and give examples

Answer 9

Biotic factors - Living components of an ecosystem eg: competition + predation

Abiotic factors - Non- living components of an ecosystem
eg: Temperature, O2 and CO2 conc, light intensity, pH and soil conditions
-Plants + animals are adapted to abiotic factors within their ecosystems

Question 10

What is the difference between intraspecific + interspecific competition?

Answer 10

Intraspecific competition- Competition between members of same species. Factors which they compete for: food, water, light, mates, shelter, minerals

Interspecific- Competition between members of different species for same limited resources. The individual better adapted to the environment is more likely to succeed in competition.

Question 11

What is predation?

Answer 11

When one organism in consumed by another

Question 12

Describe the predator prey relationship

Answer 12

1- Prey have lots of food so can survive + reproduce which increases prey population
2- This means there is more food for predators so predators eat prey so prey population decreases and predator population increases
3- Fewer prey available so predator population decreases as unable to survive and reproduce
4- Fewer predators means fewer prey eaten so more survive + reproduce so prey population increases + cycle repeats

Question 13

What is succession?

Answer 13

Ecosystems are dynamic systems.
Succession is the gradual directional change of organisms over time via a stages (seres)

Question 14

What are the two types of succession?

Answer 14

Primary succession: When plants grow where no plants have grown before
Secondary succession: When plants grow where there has been a previous population. It occurs in a previously colonised area - these will have been destroyed eg. by fires. (succession grows at a later stage)

Question 15

Explain primary succession

Answer 15

-Area is first colonised by pioneer species such as mosses or lichens which are adapted to survive in harsh conditions. Must be able to grow quickly + short lived.
-As organisms die, they’re decomposed by microorganisms thus adding humus which leads to the formation of soil over time - makes environment more suitable for more complex organisms. Soil becomes richer in minerals overtime allowing larger plants (shrubs) to grow.
-Climax community is the final stages of succession - stable community.

Question 16

What is conservation?

Answer 16

-The management of the Earth’s resources + it involves the management of succession. Also involves the preservation of organisms.
- It is a dynamic process (needs to constantly adapt to changing environmental, social + political pressures).
-Sometimes leads to conflict

Question 17

Explain the ways to conserve habitats + species

Answer 17

1) Can be given legal protections (in UK, habitats are preserved through legal designations + globally, endangered species are protected through the CITES agreement.

2) Populations can be increased through captive breeding programmes (often takes place in zoos) - animals can then be released into wild.

3) Succession can be managed. Succession involves disruption of ecosystems so, humans can intervene to ensure the habitat can continue to exist in current stage of succession.

4) Genetic diversity of plants can be preserved using seed banks. - They store seeds in cool + dry location so they don’t germinate. Can be used to reseed a plant population if they go extinct.

5) Quotas can manage fishing stocks. Quotas regulate how many fish can be caught in a specific area. They aim to prevent overfishing (which can lead to extinction) .

Question 18

What are the limitations of conservation strategies?

Answer 18

• Protected areas: Often direct conflict between stakeholders. Conservationists wish to preserve area whilst inhabitants wish to make a living from it (agriculture/tourism)
• Captive breeding programmes: Some species have difficulty mating in artificial surroundings (zoos). Releasing animals back into wild may be unsuccessful or could introduce new disease into native population.
• Seed banks: Seeds need to be constantly tested for viability (expensive + time consuming)
• Fishing quotas: Unpopular with fishermen as they limit potential revenue.

Question 19

What is abundance and distribution?

Answer 19

-Abundance is the number of individuals of a particular species in a given area
-Distribution is the location of a particular species in a given area

Question 20

Why does most ecological research use random sampling?

Answer 20

Would be too laborious + time consuming to investigate all individuals in given population.
Also helps to avoid bias (using random number generator).

Question 21

How can you estimate the size of a population using quadrats?

Answer 21

-Quadrats + transects are used when looking at non-motile organisms (plants/ slow moving animals)
- Quadrat is a square frame + is placed on ground at sampling sites
-Species frequency (how often species appear) + Percentage cover (how much of quadrat is occupied by a species) may be recorded)

Question 22

How can you estimate the size of a population using transects?

Answer 22

-Transect is a line that crosses a habitat - used to investigate distribution of species throughout habitat.
-Belt transects: quadrats placed alongside each other
-Interrupted transects: quadrats placed at regular intervals along transect

Question 23

How can you capture more motile animals?

Answer 23

-Use of specialised equipment eg. Sweep net for flying insects, fishing net for aquatic organisms + pitfall trap for terrestrial insects (container buried in ground, insects will fall into container).

Question 24

Explain how the size of a population can be estimated using Mark-Release Recapture

Answer 24

1) Sample of species are caught + number of individuals is counted
2) These are then marked so they can be readily identified (marking must be harmless so doesn’t reduce their capability)
3) Organisms are released back into their habitat - a period of time must now pass to ensure all marked individuals successfully reintegrate with main population
4) 2nd sampling of population is undertaken
5) Both the total number of individuals in 2nd sample, as well as number of individuals in 2nd sample that were marked are counted.

Question 25

What is the equation to estimate the population size?

Answer 25

P = N1 x N2
____________
M2

P= size of population
N1= number of individuals caught in 1st sample
N2= number of individuals caught in 2nd sample
M2= number of individuals in 2nd sample that were marked

Question 26

What are the assumptions when using mark-release recapture?

Answer 26

• During the time of the study there are no birth, death, or migratory factors that could affect population
• Marked sample successfully reintegrated with main population
  -The survivability of marked sample wasn’t affected in any way