Populations In Ecosystems

Question 1

What is a community?

Answer 1

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

Question 2

What is an ecosystem?

Answer 2

Community + abiotic components of an environment

Question 3

What are biotic factors?

Answer 3

Impact of interactions between organisms

Question 4

What different ways can you use to estimate a population size?

Answer 4

Quadrats
Belt transect
Mark-release-recapture

Question 5

What are quadrats used for?

Answer 5

To sample slow or non-motile organisms

Question 6

What is the process of using quadrats to estimate population size?

Answer 6

• place 2 tape measures at a right angle to create a gridded area to take samples from
• use a random number generator to generate coordinates to avoid bias
• place quadrat on coordinate + count abundance or percentage cover of species
• repeat approximately 30x

Question 7

What is a belt transect used for?

Answer 7

Used instead of random sampling also for slow or non-motile organisms

Question 8

What is the process of using a belt transect to estimate population size?

Answer 8

• tape measure placed through a non-uniform ecosystem like a rocky beach
• quadrat is place at regular intervals along the transect to measure the impact of changes in the environment

Question 9

What is the frequency in quadrats?

Answer 9

How many squares the species is present in

Question 10

What is the density of a quadrat?

Answer 10

Every individual of the species is counted

Question 11

What is the percentage cover of a quadrat?

Answer 11

Estimate the percentage of the whole quadrat that is covered by the species

Question 12

What is the mark-release-recapture system for?

Answer 12

For estimate the population size of motile organisms

Question 13

What is the process of the mark-release-recapture system?

Answer 13

• animals are trapped + marked by a substance that doesn’t affect predation or reproduction
• released + left to distribute themselves in the population
• recaptured a few days later and second sample taken
• repeated approximately 10x

Question 14

What is the formula for population size?

Answer 14

Population size = size of 1st sample * size of 2nd sample / number of marked recapture

Question 15

What properties does the marking substance have to have?

Answer 15

Needs to be non-toxic, weather proof and can’t impact predation or reproduction

Question 16

What assumptions have to be made when using the mark-release-recapture technique?

Answer 16

• enough time for organisms to distribute themselves
• no migration
• no births or deaths

Question 17

What is primary succession?

Answer 17

Change in the ecological community over time

Question 18

What is the process of primary succession?

Answer 18

1 pioneer species colonises bare rock or sand
2 species adapted to survive harsh abiotic condition + change abiotic factors to be less harsh through death/decomposition
3 moss + smaller plants can now survive + increase depth of the nutrient density in the soil as they die
4 continues and larger plants can survive + further change to environment
5 each new species may change the environment in a way that previous species can no longer survive since they become outcompeted
6 changes result in a less hostile environment + increase biodiversity
7 final stage of succession is a climax community

Question 19

How are habitats conserved in terms of succession?

Answer 19

Succession is managed often by preventing a climax community so there is a wider variety of habitats and therefore a higher species diversity
Provides conflict between human needs and conservation

Question 20

What is an example of conservation?

Answer 20

Coppicing trees - still get wood but trees are preserved and can regrow