Populations Flashcards

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
What is predation?
When one organism consumes another
26
Why is there always more prey than predator?
Not enough energy in food chain to support large predator population
27
What is an ecosystem?
All the interacting biotic and abiotic features in a specific area
28
Why is it hard to prove that competition is the reason for variations in population?
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
Why are periodic population crashes important in evolution?
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
Explain why a statistical test was necessary in analysing the results.
To calculate the probability that the data was down to chance. Thus, you know if you should accept or reject the null hypothesis.
31
Explain why it was important to check the repeatability of the measurements.
Ensure its reliable | Easier to spot anomalies
32
You could use a scatter diagram to check the repeatability of measurements made by two observers. Describe how.
Plot one set of results against the other Compare the correlations
33
What information is required in order to calculate the growth rate of a population?
The population change Birth rate Death rate In a given time
34
Show equation for population that stays the same b=birth D=death E=emigration I=immigration
B + I = D + E
35
Show equation for a population that is increasing in size B=births D=deaths E=emigration I=immigration
B + I > D + E
36
What 2 events contributed most to human population expansion
Development of agriculture And Industrial revolution
37
What is the demographic transition?
Change in societies from high birth rate and low life expectancy to low birth rate and high life expectancy
38
What do age population pyramids show us
Information on the future trends of different populations
39
Describe a stable population
Birth and death rate in balance, no increase or decrease
40
Describe an increasing population
High birth rate and fewer older people
41
Describe a decreasing population
Lower birth rate and lower death rate
42
Describe the shape of the age population pyramid of a typical less economically developed country
Large base, small top Due to high birth rate and high death rate
43
Describe the shape of age population pyramid typical of certain economically developed countries
Almost straight up and down Due to lower birth rate and lower death rate
44
How do you work out life expectancy
Calculate from a survival curve Age at which 50% of individuals in population are sill Alive
45
How do you work out life expectancy from a survival curve
Go to 50% of the population then along and down to the age
46
Reasons for stage 2 in demographic transition of the human population
Agricultural revolution = no longer relied on hunting and gathering food Medical revolution = medical technology spread & eliminated causes of death
47
Reason for stage 3 of demographic transition of human population
Families less reliant on children as source of wealth so more family planning means less births