1 • Populations And The Environment

Question 0

What is a community?

Answer 0

A community is all the populations of different organisms living and interacting in a particular place at the same time

Question 1

What is a population?

Answer 1

A population is a group of interbreeding organisms of one species in a hábitat

Question 2

What is a habitat?

Answer 2

A habitat is the place where a community of organisms lives

Question 3

What is a niche?

Answer 3

A niche is where an organism lives and what it does there

Question 4

Factors to consider when using quadrats

Answer 4

• Size: larger spaces require larger quadrats
• Number: the larger the sample size, the more reliable the results will be
• Position: Random, to avoid bias, and get statsitically significant results

Question 5

Random sampling

Answer 5

• Lay out a long tape at right angles
• Along two sides of the study area
• Obtain random coordinates (computer)
• Place quadrat and record the species whitin it

Question 6

Sampling along transects

Answer 6

• String/tape across the ground in a straight line

* Any organism touching the line is recorded

Question 7

Measuring abundance

Answer 7

• Frequency: Gives idea of species present and general distribution but does not provide information on density and detail distribution
• Percentage Cover: Estimate of the area within a quadrat that a particular plant species covers. Rapid and no need to count. Not useful where organisms overlap in layers

Question 8

Mark-release-recapture assumptions

Answer 8

• The mark or label is not lost or rubbed off
• The method of marking is not toxic or makes the individual more obvious for predators
• The are few if any deaths and births
• No emigration or immigration
• The marked individuals release distribute evenly and have enough time to do so

Question 9

Population growth curves

Answer 9

• Lag phase: slow growth
• Log phase: rapid growth/ Exp growth
• Stationary phase: Overshoot/ no growth/ small fluctuations due to food suply or increased predation

Question 10

Define abiotic and biotic factors

Answer 10

• Abiotic: Non-biological factor that makes up part of an ecosystem
• Biotic: Biological factor that makes up part of an ecosystem

Question 11

Intraspecific competition

Answer 11

Individuals of the same species competing with one another for resources such as food, water, breeding sites

Question 12

Interspecific competition

Answer 12

• Individuals of different species competing for resources.
• Same niche: one will have a competitive advantage over the other
• This one will increase in population while the other will diminish

Question 13

What is it called when one species ultimately eliminates the other because it uses the resources more effectively and has a competitive advantage?

Answer 13

Competitive Exclusion Principle

Question 14

What is a predator?

Answer 14

A predator is an organism that feeds on another organism know as their prey

Question 15

Effect of predator-prey relationship on population size

Answer 15

• Predators eat prey, thereby reducing population of prey
• Fewer prey, increases competition for prey left
• Predators population decreases
• Fewer predators, fewer prey are eaten
• Prey population increases
• More prey, predator population increases

Question 16

Population growth

Answer 16

Pg = (births+immig) - (deaths+emig)

Question 17

Factors affecting birth rates

Answer 17

• Economic conditions
• Cultural and religious backgrounds
• Social pressures and conditions
• Birth control
• Political factors

Question 18

Factors affecting death rates

Answer 18

• Age profile
• Life expectancy at birth
• Food supply
• Safe drinking water and effective sanitation
• Medical care
• Natural disasters
• War