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Biology Unit 4 > Populations > Flashcards

Populations Flashcards

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1
Q

What is an ecosystem?

A

An ecosystem is made up of all the interacting biotic and abiotic factors features in a specific area.
Two processes must be considered:
-Flow of energy through the system
-The cycling of elements within the system

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2
Q

What is an abiotic factor?

A

Non-living components that make up an ecosystem

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3
Q

What is an biotic factor?

A

Living components that make up an ecosystem

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4
Q

What is a population?

A

A group of interbreeding organisms of one species in a habitat

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5
Q

What is a community?

A

All populations of different organisms living and interacting in a particular place at the same time.
E.g. Oak woodland - Oak trees, bluebells and ladybirds

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6
Q

What is a habitat?

A

Place where a community of organisms live, in an ecosystem there are many habitats

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7
Q

What is a microhabitat?

A

Smaller units of a habitat with each having their own microclimate e.g. mud at the bottom of a stream

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8
Q

What is a ecological niche?

A

Describes how an organism fits into the environment- refers to where it lives and what it does there
No two species occupy the same niche.

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9
Q

What is the abundance of a species?

A

Counting the number of individuals of a species in a given space

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10
Q

What method would you use to carry out random sampling?

A

Frame quadrats and point quadrats

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11
Q

What method would you use to carry out systematic sampling?

A

Transects

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12
Q

What are the three things to consider when using quadrats?

A
  • Size of quadrat to use
  • Number of sample quadrats to record within the study area
  • The position of each quadrat in each study area
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13
Q

How do you use a quadrat to carry out random sampling?

A
  1. Lay out two long tape measures at right angles along two sides of the study area
  2. Obtain coordinates by using random number generator
  3. Place a quadrat at the intersection of each pair of coordinates and record the species within it
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14
Q

What is a line transect?

A

Uses a line of string or tape stretched across the ground in a straight line, any organism that crosses the line is recorded.

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15
Q

What is a belt transect?

A

Two parallel lines of tape and the species occurring within the belt is recorded.

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16
Q

What is the mark-release-recapture technique?

A

Used to measure abundance of species

  1. Known number of animals are caught
  2. Marked without being harmed
  3. Then released back into their original environment
  4. Some time later a given number of individuals are randomly collected
  5. The number of individuals previously marked is recorded.
17
Q

What is the equation for the mark-release-recapture technique?

A

Number of marked individuals recaptured

18
Q

What things does the mark-release-recapture technique rely on?

A
  • The marked individuals released from the first sample have sufficient time to distribute themselves amongst the remainder of the population
  • The population has a definite boundary so there is no immigration into or emigration out of the population
  • There are few, if any deaths and births within the population
  • The method of marking is not toxic to the individual
  • The marking is not lost or rubbed off during the investigation
19
Q

What is the usual pattern of growth of a population curve?

A
  1. Period of slow growth as the small number of individuals reproduce to slowly build up their numbers
  2. Period of rapid growth where the ever-increasing number of individuals continue to reproduce , the population size doubles during each interval of time.
  3. The population growth declines until it’s size remains more or less stable, may be cyclic fluctuations due to variation in factors such as food supply or predation.
20
Q

What are the abiotic factors that influence the size of a population?

A

Temperature-enzyme denaturation
Light
pH-enzyme denaturation
water and humidity

21
Q

What is intraspecific competition?

A

Competition that occurs when individuals of the same species compete with another for resources such as food, water and breeding sites.

22
Q

What is interspecific competition?

A

Competition that occurs when individuals of different species compete for resources as they occupy the same niche.

23
Q

What is the competitive exclusion principle?

A

When two species have the same niche but one species becomes outcompeted so that one species is completely removed from the community.

24
Q

What is predation?

A

When one organism is consumed by another

25
Q

How does a predator-prey relationship affect a population size?

A
  1. Predators eat their prey which reduces prey population
  2. With fewer prey available the predators are in competition with each other
  3. Predator population decreases as they can’t obtain enough prey for survival
  4. Prey population increases again as fewer predators
  5. More prey is now available as food so the predator population increases again
26
Q

What affects a human population size?

A

Birth and death rate

Immigration and emigration

27
Q

How do you work out the population growth?

A

Population growth= (births + immigration) - (deaths + emigration)

28
Q

How do you work out the percentage population growth rate in a given period of time?

A

Population change during the period/ population at the start of the period
*100

29
Q

What factors affect birth rate?

A
  • Economic conditions
  • Cultural and religious backgrounds
  • Social pressures and conditions
  • Birth control
  • Political factors
30
Q

What factors affect death rate?

A
  • Age profile
  • Life expectancy at birth
  • Food supply
  • Safe drinking and effective sanitation
  • Medical care
  • Natural disasters
  • War
31
Q

How do you calculate the birth rate?

A

Birth rate= number of births per year/total population in the same year
*1000

32
Q

How do you calculate the death rate?

A

Death rate= number of deaths per year/total population in the same year
*1000

33
Q

What is demographic transition?

A

A change in life expectancies in societies it leads to a levelling off of the population and re-establishment of the typical population growth curve

34
Q

What is a survival curve?

A

It plots the number of individuals alive as a function of time and plots the percentage of the population still alive following a particular event e.g. medical operation or the onset of an disease

35
Q

How do you work out the average life expectancy?

A

Look at the survival curve and work out where 50% is and see how many individuals in a particular population are still alive

Biology Unit 4 (2 decks)

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