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A2 Biology > Populatipns And Ecosystems > Flashcards

Populatipns And Ecosystems Flashcards

1
Q

What is a population?

A

All the organisms of one species in a habitat

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2
Q

What is a community?

A

Populations of different species in a habitat that make up a community

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3
Q

What is an ecosystem?

A

All the organisms living in a particular area and all the abiotic conditions

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4
Q

What is meant by abiotic conditions?

A

The non-living features of an ecosystem e.g. Temperature

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5
Q

What is meant by biotic conditions?

A

The living features of an ecosystem e.g. Predators

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6
Q

What is a niche?

A

The role of a species within its habitat

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7
Q

What is an adaptation?

A

A feature that members of a species have that increase their chance of survival and reproduction

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8
Q

What happens if two species try to occupy the same niche?

A

They compete with each other, as a niche can only be occupied by one species

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9
Q

What is meant by abundance?

A

The number of individuals of a species in a given area

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10
Q

What type of sampling do quadrats involve?

A

Random sampling

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11
Q

What time of sampling do transects involve?

A

Systematic sampling

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12
Q

What is meant by frequency in sampling?

A

The number of samples a species is recorded in

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13
Q

What is percentage cover and what is it used for?

A

How much of the investigated area is covered by a species, and is used for plants only

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14
Q

What are the main steps when conducting a sample?

A 
## choose an area
## make sample random e.g. Random number generator to avoid bias 
## use appropriate technique(quadrats,transects)
##repeat samples for a more reliable estimate for the whole area
##carry out necessary calculations (e.g. % cover, mean abundance)
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15
Q

What 3 factors need to be considered when using quadrats?

A

Size , position and number of sample quadrats to use

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16
Q

What are the 3 types of transects and what do they involve?

A
  • Belt - Quadrats placed next to each other along transect to work frequencies and % cover
  • Line - Tape measure placed along transect and species that touch it are recorded
  • Interrupted - Take measurements at intervals
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17
Q

What are the steps of mark-release-recapture?

A 
## Capture sample of species using an appropriate technique
## Give each organism a harmless marking 
## Released them back into their habitat 
## Allow enough time before taking a second sample from the same population 
## Count number of marked organisms in second sample
## calculate estimated population size
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18
Q

What assumptions do the mark-release-recapture technique rely on?

A
  • Marked sample has had enough time to mix back with population
  • Marking hasn’t affected individuals chances of survival and is still visible
  • Number of births,deaths and migrations are small during sampling period
19
Q

How is the estimated population size calculated?

A

(No. Caught in 1st sample X No. Caught in 2nd sample)
___________________________________
No. Marked in 2nd sample

20
Q

How does population size vary?

A

Because of abiotic and biotic factors

21
Q

How do abiotic factors affect population size?

A

When ideal for a species, they can grow fast and reproduce successfully e.g. Optimum temperature for metabolic reactions , which increases size of population

However when they aren’t ideal, they can’t grow or reproduce as well, causing size of population to decrease

22
Q

What 3 biotic factors affect population size?

A

Inter specific competition, Intraspecific competition and predation

23
Q

What is interspecfic competition and how does it affect population size?

A

Competition between members of different species e.g. For food or space , if two species are competing but one is better adapted than the other, less adapted species is out competed and won’t be able to exist along size the other well adapted species

24
Q

What is Intraspecific competition and how does it affect population size?

A

Competition between members of the same species, when they compete for the same resources as the size of the population’s needs cannot be meet by availability, population declines. A smaller population means that there is less competition for resources and so population starts to increase again

25
Q

What is predation and what is the effect of the predator-prey relationship on population size?

A

Where an organisms kills and eats another organism. Population sizes of predators and preys are interlinked because as the population of one changes , it causes the other population to change.

More predators = fewer prey
Fewer prey = predators compete
Reduction of predator population = fewer prey eaten
Prey population increases = predator populations begins to increase again

26
Q

How is human population growth calculated (per 1000 / year)?

A

(Births + immigration) - (deaths + emigration)

27
Q

What is birth rate?

A

Number of live births each year for every 1000 people

28
Q

What is death rate?

A

Number of deaths per year per 1000 people

29
Q

How is percentage population growth calculated in a given period?

A

Population change during
____________________________
Population at start

X 100

30
Q

What two major events led to an explosion in human population?

A

Agriculture and manufacturing development (industrial revolution)

31
Q

What can cause temporary reversals in population trends?

A

Wars, disease and famine

32
Q

What is immigration?

A

Individuals join a population from outside

33
Q

What is emigration?

A

Individuals leave a population

34
Q

What factors affect birth rate?

A
  • economic conditions (e.g. LIC have higher birth rates due to lack of birth control)
  • cultural and religious reasons
  • social pressures
  • birth control
  • political factors (e.g. China’s one child policy)
35
Q

What factors affect death rate?

A
  • Age profile - the greater amount of elderly in a population the higher the death rate
  • life expectancy at birth
  • food supply
  • clean sanitation and drinking water
  • medical care
  • natural disasters
  • war
36
Q

What is the demographic transition model?

A

A graph that shows changes in birth rate, death rate and total population size for a human population over a long period of time and is divided into 5 stages

37
Q

What are the 5 stages of the demographic transition model and what do each one show about the population at that point?

A

STAGE 1 - BR and DR fluctuate at high level and population stays low, due to no birth control and poor health care / sanitation

STAGE 2 - DR falls BR remains high and population increases rapidly, improvement of conditions but still little birth control

STAGE 3 - BR falls rapidly and DR falls slowly and population increases at slower rate. More birth control is used and economy relies less on agriculture

STAGE 4 - BR and DR fluctuate at low level and population remains stable but high. Parents having fewer children as less money is able to raise them as there is an increase in disposable income

STAGE 5 - BR falls and DR stable, population decreased larger generation of elderly and parents having fewer children to care for elderly parents

38
Q

What does a stable population show?

A

Birth rate and death rate balanced so no increase or decrease In population

39
Q

What does an increasing population show?

A

High birth rate and fewer old people

40
Q

What does a decreasing population show?

A

Lower birth rate and lower mortality rate, more older people

41
Q

What is average life expectancy?

A

The age at which 50% of the individuals in a population are still alive, age a person born is expected to live to and worked out by calculation average age people die in a population

42
Q

What do survival curves show?

A

The percentage of all the individuals that were born in a population that are still alive at any given age, and so gives a survival rate for any age

43
Q

What is a habitat?

A

The place where an organism lives

A2 Biology (12 decks)

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