B19 - Populations and ecosystems

Question 1

What are ecosystems?

Answer 1

Ecosystems are dynamic systems made up of a community and all the abiotic factors of its environment. There is little or no loss or gain between one and other ecosystems

Question 2

What is intraspecific competition?

Answer 2

Where individuals of the same species compete for food, water, breeding sites, etc. The availability of such resources will determine the size of the population. It will also determine the degree of competition

Question 3

What is interspecific competition?

Answer 3

Competition between individuals of different species

Question 4

What is a niche?

Answer 4

A niche describes how an organism fits into its environment. It refers to the role and position of the organism within its habitat, where it lives, what it does, how it meets its need for food, shelter, mate etc

Question 5

What is the carrying capacity

Answer 5

The maximum population size an ecosystem can support due to limiting factors. E.g: Availability of food, light, water, oxygen, mineral ions, predators

Question 6

What does having a competitive advantage over competitors mean?

Answer 6

One population will have a competitive advantage over the other. This population will increase in size while the other decrease
If conditions don’t change, the disadvantaged species can be completely removed - competitive exclusion principle

Question 7

What are abiotic factors?

Answer 7

An abiotic factor is a non-living part of an ecosystem that shapes its environment

Question 8

What are examples of abiotic factors that can affect population size?

Answer 8

Temperature
Light
pH
Water and humidity

Question 9

What is a predator?

Answer 9

An organism that feeds on another organism, known as prey

Question 10

When using quadrats how can you use random sampling and avoid bias?

Answer 10

1. Lay out 2 long tape measure at right angles, along 2 sides of the study area
2. Series of coordinates randomly generated
3. Place the quadrats at the intersection of the coordinates

Question 11

What type of sampling is using a transect?

Answer 11

Systematic

Question 12

What is the formula for Mark-release-recapture?

Answer 12

Population size estimate = (Size of first sample x size of second sample) / Marked animals recaptured

Question 13

What are assumptions made when using Mark-release-recapture?

Answer 13

• Proportion of labelled individuals to unlabelled is the same in the second sample and in the whole population
• Marked individuals distribute evenly
• No immigration, no emigration
• Few, if any, births and deaths
• Marking is non-toxic and doesn’t affect individual in any way
• Marker is not lost or removed

Question 14

What is succession?

Answer 14

Describes changes over time in the species that occupy a particular area

Question 15

What is a pioneer species?

Answer 15

They make up pioneer community, first ones to colonise an inhospitable environment

Question 16

What is a climax commmunity?

Answer 16

Ultimate, stable community with a balanced equilibrium of species (few, if any, species replacing established ones). Abiotic factors will determine the dominant species

Question 17

What are features of a pioneer species?

Answer 17

Asexual reproduction
Vast quantities of wind-spread seed/spores
Rapid germination
Ability to photosynthesise
Ability to fix nitrogen
Tolerance to extreme conditions

Question 18

What does a series of successional changes lead to?

Answer 18

At each stage new species colonise the area and they may change the environment which can lead to interspecific competition
A series of successional changes which alter abiotic environment and helps forming new communities and increasing biodiversity

Question 19

Which is faster primary or secondary succession?

Answer 19

Primary succession - slow process
Secondary succession - fast process. When the land, that already sustained life suddenly changes