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Biology Unit 4 > Populations > Flashcards

Populations Flashcards

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1
Q

What is a population?

A

Group of interbreeding organisms of one species in a habitat

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2
Q

What is a community?

A

All the populations of different organisms living and interacting in a particular place at the same time

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3
Q

What is a habitat?

A

A place where a community of organisms live

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4
Q

What is a microhabitat?

A

Smaller units within each habitat

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5
Q

What is a niche?

A

How an organism fits into the environment (ie where it lives).

Includes both biotic and abiotic conditions required for it to survive, reproduce and maintain a populations

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6
Q

Name biotic factors

A 
Human influence 
Competition
Predation
Dispersal
Pollination
Mimicry 
Antibiosis
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7
Q

Name climatic abiotic factors

A 
Light
Water
Temperature
Humidity
Air currents
Water currents
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8
Q

Name edaphic abiotic factors

A 
Topography
Mineral content
Air content
Biotic content
Organic content
Water content
PH
Temperature
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9
Q

How would you use a quadrat when counting moss?

A

Can’t count so estimate the percentage of the grid it covers

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10
Q

Describe how you would estimate the number of XXX in a small woodland?

A 
Split area in sections
Find random coordinates
Count frequency in quadrat
Calculate mean per quadrat
Mean per quadrat x by number of sections
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11
Q

When do you use transects instead of guadrats

A

If you want to see changing conditions

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12
Q

If you’ve observed an area using a transect and want to see if it’s valid what could you do?

A

Repeat in a slightly different place e.g. A meter along

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13
Q

What are the problems when collecting data on animals?

A

They move

Their behaviour changes

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14
Q

Describe the mark, release and recapture method

A 
Capture a sample
Count them
Mark them
Release them
Later, randomly select second sample
Count how many marked

Estimated population = 1st sample xs 2nd sample divided by number of marked recaptured in 2nd sample

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15
Q

What could effect the mark, release recapture method?

A

If they don’t mix evenly when put back

Behaviour changes

Population changes (eg births/deaths)

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16
Q

Suggest how the shape of an animals mouth is an adaptation to its niche

A

Different shape mouth catches different foods

Competition between species reduced

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17
Q

What abiotic factors can effect the population size and how?

A

Water (not many species adapted for dry conditions & humidity effect transpiration rate & water evaporation from mammals)

Temperature (denture enzymes or slow down rate of reaction)

Light (increase photosynthesis so grow more so more food for animals)

PH (effect enzyme action)

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18
Q

What is the density dependence growth?

A

Population grows then remind stable after reaching a certain size

Limiting factors usually food and toxic waste accumulation

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19
Q

Describe the 3 parts to a graph of number of organisms against time

A 
Slow growth
Then
Rapid growth (as plenty resources)
Then
No growth, stable state & possibly small fluctuations due to changes in factors eg food supplies
20
Q

What is density independence growth?

A

Population grows and reminds stable until some factor causes dramatic reduction in size eg disease

21
Q

What is intraspecific competition?

A

Same species compete for resources

22
Q

What is interspecific competition?

A

Different species compete for resources

23
Q

What is the competitive exclusion principle

A

2 species in the same niches compete
1 has an advantage so increases size
Other decreases in size
If conditions stay the same, 2nd species will be completely removed

24
Q

Why can’t 2 species remain in the exact same niche?

A

Resources or limited

Competitive exclusion principle may occur

25
Q

What is predation?

A

When one organism consumes another

26
Q

Why is there always more prey than predator?

A

Not enough energy in food chain to support large predator population

27
Q

What is an ecosystem?

A

All the interacting biotic and abiotic features in a specific area

28
Q

Why is it hard to prove that competition is the reason for variations in population?

A

Many other factors influence population size

Data on natural population sizes are hard to obtain so not always reliable

There is a time lag in many cases of competition so change may be due to competition that took place years earlier

29
Q

Why are periodic population crashes important in evolution?

A

They create a selection pressure - only individuals who can escape predators or deal with disease or an adverse climate, will be able to survive and reproduce. Thus the population evolves to be better adapted.

30
Q

Explain why a statistical test was necessary in analysing the results.

A

To calculate the probability that the data was down to chance. Thus, you know if you should accept or reject the null hypothesis.

31
Q

Explain why it was important to check the repeatability of the measurements.

A

Ensure its reliable

Easier to spot anomalies

32
Q

You could use a scatter diagram to check the repeatability of measurements made by two observers. Describe how.

A

Plot one set of results against the other

Compare the correlations

33
Q

What information is required in order to calculate the growth rate of a population?

A

The population change
Birth rate
Death rate
In a given time

34
Q

Show equation for population that stays the same

b=birth
D=death
E=emigration
I=immigration

A

B + I = D + E

35
Q

Show equation for a population that is increasing in size

B=births
D=deaths
E=emigration
I=immigration

A

B + I > D + E

36
Q

What 2 events contributed most to human population expansion

A

Development of agriculture
And
Industrial revolution

37
Q

What is the demographic transition?

A

Change in societies from high birth rate and low life expectancy to low birth rate and high life expectancy

38
Q

What do age population pyramids show us

A

Information on the future trends of different populations

39
Q

Describe a stable population

A

Birth and death rate in balance, no increase or decrease

40
Q

Describe an increasing population

A

High birth rate and fewer older people

41
Q

Describe a decreasing population

A

Lower birth rate and lower death rate

42
Q

Describe the shape of the age population pyramid of a typical less economically developed country

A

Large base, small top

Due to high birth rate and high death rate

43
Q

Describe the shape of age population pyramid typical of certain economically developed countries

A

Almost straight up and down

Due to lower birth rate and lower death rate

44
Q

How do you work out life expectancy

A

Calculate from a survival curve

Age at which 50% of individuals in population are sill Alive

45
Q

How do you work out life expectancy from a survival curve

A

Go to 50% of the population then along and down to the age

46
Q

Reasons for stage 2 in demographic transition of the human population

A

Agricultural revolution = no longer relied on hunting and gathering food

Medical revolution = medical technology spread & eliminated causes of death

47
Q

Reason for stage 3 of demographic transition of human population

A

Families less reliant on children as source of wealth so more family planning means less births

Biology Unit 4 (14 decks)

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