Populations within Ecosystems

Question 1

What is a community?

Answer 1

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

Question 2

What is an ecosystem?

Answer 2

The interaction between a community biotic and the abiotic parts of the environment.

Question 3

What is a habitat?

Answer 3

part of an ecosystem in which a particular organism lives

Question 4

What is a niche?

Answer 4

organisms role within their ecosystem (e.g their position within the food web and habitat)
- each species occupies their own niche, no two species can share niche OR they’ll go into competition with each other

Question 5

What is a species?

Answer 5

A group of organisms that can interbreed to produce fertile offspring

Question 6

How do abiotic factors affect biodiversity?

Answer 6

The changes that species produce in their abiotic environment can actually result in a less hostile environment
As a result, this can change or sometimes increase the biodiversity within that environment

Question 7

What is carrying capacity?

Answer 7

The maximum stable population size of a species that an ecosystem can support.

Question 8

What abiotic factors limit population size?

Answer 8

• light availability
• water supply
• temperature
• amount of space available
• soil pH

Question 9

What biotic factors limit population size?

Answer 9

• interspecific competition → members of different species competing for the same resource that is limited in supply
• intraspecific competition →members of the same species in competition for resources and a mate
• predation → in a stable community, the numbers of predators and prey rise and fall in cycles, limiting the population sizes of both predators and prey

Question 10

How to estimate size of population? (non-motile organisms)

Answer 10

Transects + Quadrats
1. Lay quadrats randomly or along a transect
2. Count number of species present and calculate a mean
3. Calculate this as a percentage (i.e. percentage cover)

Question 11

3 Factors of Predator Prey Relationships over time

Answer 11

1. Size of the predator prey population fluctuate: increase in prey is more food for predators- predators get more food so reproduce more SO MORE PREDATORS
   - population of prey decreases causing SO not enough food for predator SO predator decreases
2. There will be more predators than prey: Prey populations will always peak at higher point → predators are further along the food chain what they eat will contain less energy due to energy loss at each trophic level) SO predator would need to eat multiple prey
3. Size of the populations will always change in the prey and then in the predators: increase in predator population after a while due to lag time.

Question 12

How to estimate size of population? (motile organisms)

Answer 12

Mark - Release - Recapture
1. The first large sample is taken. As many individuals as possible are caught, counted and marked in a way that won’t affect their survival
2. The marked individuals are returned to their habitat and given sufficient time to randomly mix with the rest of the population
3. The number of marked and unmarked individuals within the second sample are counted
4. The proportion of marked to unmarked individuals is used to calculate an estimate of the population size
N = (n1 × n2) ÷ m2
n1 = number of marked released
n2 = number of individuals in second sample
m2 = number of marked in second sample

Question 13

What is succession?

Answer 13

the change in the ecological community overtime

Question 14

What is a seral stage?

Answer 14

each stage where there is a noticeable change in the community

Question 15

What is primary succession?

Answer 15

The process that occurs when newly formed or newly exposed land (with no species present) is gradually colonised by an increasing number of species.

Question 16

Outline the stages of primary succession.

Answer 16

1. Seeds and spores that are carried by the wind land on the exposed rock and begin to grow, these are known as pioneer species
2. As these pioneer species die and decompose, humus forms a basic soil
3. Small plants and shrubs outcompete pioneer species and colonise land
4. As these small plants and shrubs die and decompose, the new soil becomes deeper and more nutrient-rich, allowing larger plants and shrubs, as well as small trees, that require deeper, more nutrient-rich soil
5. Finally, the soil is sufficiently deep, contains enough nutrients and can hold enough water to support the growth of large trees, this is known as the climax community

Question 17

How does the environment change as a result of succession?

Answer 17

• deeper soil
• more nutrient rich soil
• increased species biodiversity
• more water content in soil

Question 18

How to manage succession?

Answer 18

• conservation of intermediate species in succession
• grazing animals
• managed burning

Question 19

Outline the stages or primary succession

Answer 19

1. Pioneer species are adapted to survive in harsh/hostile abiotic factors → through death and decomposition they change the abiotic factors to become less harsh/hostile and form a thin layer of soil called humus
2. mosses and smaller plants can now survive & change environment further

Question 20

general trend of primary succession

Answer 20

• changes that organisms produce in abiotic environment results in a less hostile environment & increased biodiversity- environment is more stable, abiotic factors are now favourable
• each species changes the environment making it less suitable for previous species SO each existing species is outcompeted by a new species colonising

Question 21

What is a climax community?

Answer 21

the stable, final community that makes uo a final stage of succession
- abiotic factors overtime

Question 22

What is secondary succession?

Answer 22

climax community gets disrupted and plants are destroyed
- succession starts again but doesn’t start from bare rock seral stage