Distribution and abundance + sucession

Question 1

what are biotic and abiotic factors?

Answer 1

biotic factors are living factors e.g. predation, competition for resources and availability of food
abiotic factors are non living factors e.g. light intensity, temperature, wind speed, edaphic factors ( pH, mineral contents )

Question 2

How is population size affected by abiotic factors?

Answer 2

In ideal abiotic factors, organisms can grow and reproduce successfully
e.g. in correct conditions, more energy can be spent on growth and reproduction increasing the population.

Question 3

How is the population size affected by biotic factors?

Answer 3

Interspecific competition- can reduce resources therefore population is limited
intraspecific competition- if resources are plentiful , leads to an increase in population, therefore leading to an increased population for the same amount of food leading to a decrease
predation- predator and prey interlinked, has external factors also

Question 4

how is distribution affected by abiotic factors?

Answer 4

organisms will only exist in areas where they can survive in

Question 5

how is distribution affected by biotic factors?

Answer 5

interspecific competition

Question 6

explain the meaning of ‘niche’

Answer 6

an organisms role in a community
a niche can only be occupied by one species
the role includes abiotic ( temperature it lives in etc.) and biotic ( what it eats etc.)

Question 7

How does the niche concept affect abundance?

Answer 7

If two species have a similar niche, they will tend to compete with each other which will lead to fewer individuals of both species

Question 8

how does the niche concept affect distribution

Answer 8

an organism can only live in an area where there role is fulfilled

Question 9

What is succession?

Answer 9

A gradual change in ecological factors and the community over time

Question 10

what causes succession?

Answer 10

a change in the abiotic or biotic factors in a habitat over time

Question 11

what are pioneer species?

Answer 11

the first species to colonise an area. They can grow in very hostile abiotic conditions e.g. no soil to retain water.
Pioneer species can include lichens, willowherb and mountain avens.

Question 12

What is primary succession?

Answer 12

an area that is newly formed or exposed

Question 13

what is secondary succession?

Answer 13

a land that has been cleared of all plants but soil remains

Question 14

what is a climax community?

Answer 14

The largest and most complex community of plants and animal. It is steady. Has the greatest number of biodiversity. It is affected by both biotic and abiotic factors.

Question 15

describe the process of succession

Answer 15

A pioneer species will colonise an area. This is done when seeds and spores are blown by the wind into the area. (first seral stage)
The pioneer species alter the environmental conditions. When the pioneer species die, they form humus(dead organic material) which improves the soil
This allows new organisms which can survive in the improved conditions to grow. When the new organisms die and decompose, the soil is improved further.
Larger plants can now inhabit the area such as shrubs.
This process will continue with larger and more complex plants inhabiting the area and becoming the dominant species.
Species diversity increases as you go on.
The final seral stage is a climax community.

Question 16

what type of conditions are present before a pioneer species colonises an area?

Answer 16

no soil to retain water
shallow soil
lack of minerals and nutrients
no shelter
becomes waterlogged

Question 17

what type of conditions are present as the abiotic and biotic factors change?

Answer 17

provide shelter
deeper soil
adds ammonium or nitrate ions to the soil
provide food

Question 18

What is a plagioclimax?

Answer 18

when succession is stopped artifically e.g. by human intervention