7.4 Populations in Ecosystems

Question 1

Ecosystem

Answer 1

A community + all the non-living factors of the environment

Question 2

Population

Answer 2

A group of organisms, of the same species, that occupy the same habitat at the same time

Question 3

Community

Answer 3

All the populations of different species living & interacting in a particular place at the same time

Question 4

Examples of biotic factors

Answer 4

Predators/prey
Disease

Question 5

Examples of abiotic factors

Answer 5

Oxygen availability
CO2 availability (plants)
Water availability
Physical space
Light intensity
Temperature
pH

Question 6

Keystone species (& give an example)

Answer 6

The niche occupied by that species plays a key role in the ecosystem
Sea otters eat sea urchins, enabling sea kelp to grow. No sea otters, more sea urchins, overgrazed kelp, species feeding off kelp die

Question 7

Competitive exclusion principle

Answer 7

Two species can’t coexist in the same habitat if they have the same niche. They will compete, and one species will win the competition.

Question 8

Considerations when using quadrats

Answer 8

1. Size of quadrat
2. # of samples to take
3. Positions of each sample
4. What to measure (frequency or % cover?)

Question 9

Things to always remember when using quadrats

Answer 9

Random sampling - avoids bias
Use random # generator to generate coordinates to place quadrats

Question 10

How to use a point quadrat

Answer 10

Lower pin through the holes, record the # of organisms touching the pin

Question 11

Mark release recapture formula

Answer 11

Estimated populations size = (# of individuals in 1st sample x # of individuals in 2nd sample) / # of marked individuals recaptured

Question 12

What happens during succession?

Answer 12

At each stage the organisms change the environment, making it less hostile and more suitable for the next stage.

The community becomes steadily more DIVERSE & STABLE over time

Question 13

What exactly do the pioneer species change in a previously uncolonised habitat?

Answer 13

the ABIOTIC CONDITIONS

Question 14

Characteristics of pioneer species

Answer 14

1. Adapted to survive in harsh conditions
2. Photosynthetic
3. Nitrogen fixation
4. Reproduce asexually
5. Fast germination rate

Question 15

Conservation

Answer 15

The management of habitats and ecosystems in a way that ensures they can continue to be used IN THE FUTURE

Question 16

Conservation is an ACTIVE & DYNAMIC process - what do these terms mean?

Answer 16

Active: carrying out active measures to change the environment
Dynamic: these active measures may change overtime

Question 17

Conservation sometimes means…

Answer 17

managing succession