Populations

Question 1

Define ecosystem

Answer 1

The interacting biotic and abiotic factors in a specific area

Question 2

Define population

Answer 2

A group of interbreeding organisms of the same species

Question 3

Define habitat

Answer 3

Place where a community lives

Question 4

Define community

Answer 4

All populations of all species in one place

Question 5

Define niche

Answer 5

Where an organisms lives and what it does there

Question 6

What do you have to consider when using quadrats to investigate a population?

Answer 6

• size of quadrats
• number of quadrats used within study area; must balance time and validity of results
• position of quadrats

Question 7

When would you use a line transact in investigating species?

Answer 7

When there is a form of transition in community (different stages of zonation in habitat)

Question 8

How can abundance be measured?

Answer 8

• frequency

- percentage cover

Question 9

Why are statistical tests carried out after data is collected?

Answer 9

• can be put into a graph; easily compared and easy to see trends
• used to calculate strength and direction of correlation

Question 10

Describe the usual pattern of growth for a natural population

Answer 10

1. Slow growth; as initially small number reproduce to build numbers
2. Rapid growth; growing number continues to reproduce
3. Stable state; growth declines due to factor such as food/predation. Graph levels out with cyclic fluctuations due to disease etc

Question 11

Why can’t a population grow indefinitely?

Answer 11

It is limited by biotic and abiotic factors

Question 12

How does temperature affect population size?

Answer 12

• each species has an optimum temp, if levels differ to far from this then enzyme denature, metabolism slows
• in warm-blooded animals, they expend more energy on maintaining constant internal temp, less energy for growth

Question 13

How does light affect population size?

Answer 13

• as light intensity increases, rate of photosynthesis increases, therefore plants grow at faster rate
• in turn, populations of animals feeding on plants grow

Question 14

What is the affect of pH on population size?

Answer 14

If it differs too far from optimum, enzymes denature

Question 15

What are the affects of water and humidity on population size?

Answer 15

• Where water is scarce, only species survuve that are adapted to living in dry conditions
• humidity affects transpiration rate; more humid it is, less transpiration occurs

Question 16

Why does interspecifc and intraspecific competition happen?

Answer 16

When 2 or more organisms/species share resources that are insufficient to support both

Question 17

What is the competitive exclusion principle?

Answer 17

Where 2 species occupy the same niche, one will have a competitive advantage, and outcompete the other. The weaker species population will diminish until it is completely removed.

Question 18

Give some adaptations of predators

Answer 18

• faster movement
• more effective camouflage
• better ways of detecting prey

Question 19

Give some adaptations of prey

Answer 19

• better camouflage
• more protective features eg.spines, poison
• concealment behaviour