3.7.4 - POPULATIONS IN ECOSYSTEMS Flashcards
give two conditions for results from mark-release-recapture investigation to be valid (2)
- marking does not affect predation
- no immigration
- sufficient time for marked individuals to mix with the population
- no/little births/deaths/breeding
what is a community? (2)
populations of different species occupying the same place at the same time
what is an ecosystem? (2)
- community and the non-living components of an environment.
- ecosystems can vary in size
what is a habitat? (1)
the part of an ecosystem in which a particular organisms lives
what is the carrying capacity? (1)
the maximum population size an ecosystem can support
what is a niche? (2)
- an organisms role within an ecosystem (including its position in food web and its habitats))
- each species occupies its own niche, governed by adaptation to both biotic and abiotic conditions
suggest one reason for conserving woodlands (1)
- conserving habitats
- protecting endangered species
- reduces greenhouse effect/global warming
succession occurs in natural ecosystems.
describe and explain how succession occurs (4)
- colonisation by pioneer species
- pioneer species changes the environment
- so environment becomes less hostile and more suitable for other species
- change/increase in biodiversity
- to climax community
the sundew is a small flowering plant, growing in wet habitats such as bogs and marshes. the soil in bogs and marshes is acidic and has very low concentrations of some nutrients. the sundew can trap and digest insects.
describe how you could estimate the size of a population of sundews in a small marsh (5)
- use a grid OR divide areas into squares/sections
- use random number generator
- count number/frequency in a quadrat
- large sample and calculate mean
- valid method of calculating total number of sundews - e.g. mean number of plants per quadrat multiplied by no of quadrats
the sundew is a small flowering plant, growing in wet habitats such as bogs and marshes. the soil in bogs and marshes is acidic and has very low concentrations of some nutrients. the sundew can trap and digest insects.
suggest and explain how digesting insects helps the sundew to grow in soil with very low concentrations of some nutrients. (2)
ANY PAIR
- digestion/breakdown of proteins
- provides amino acids
OR
- digestion of named phosphate-containing compound e.g. DNA
- provides named phosphate-containing product e.g. nucleotides
describe how you would determine the mean percentage cover for beach grass on a sand dune (3)
- random number generator to generate position of quadrats
- large number of samples
- divide total percentage by number of quadrats
dengue is a serious disease that is caused by a virus. the virus is carried from one person to another by a mosquito, A. aegypti.
one method used to try to reduce transmission of this disease is the sterile insect technique (SIT).
this involves releasing large numbers of sterile (infertile) males into the habitat.
explain how using the SIT could reduce transmission of dengue (2)
- compete for resources OR intraspecific competition
- reduces population
dengue is a serious disease that is caused by a virus. the virus is carried from one person to another by a mosquito, A. aegypti.
one method used to try to reduce transmission of this disease is the sterile insect technique (SIT). this involves releasing large numbers of sterile (infertile) males into the habitat.
describe how the mark-release-recapture method could be used to determine the population of A. aegypti at the start of the investigation (3)
- capture, mark and release
- leave time for mosquitos to disperse before second sampling
- population = number in first sample x number in second sample divided by number of marked in second sample
the release of radiation-sterilised mosquitos has not been very successful in controlling the transmission of dengue.
suggest one reason why (1)
radiation affects their courtships/survival/lifespan
give two features of a climax community (2)
- same species/stable community present over a long time
- abiotic factors constant
- populations stable (around carrying capacity)
describe how you would investigate the effect of an invasion by a non-native species of a plant (a biotic environmental factor) over many years on the abundance of a native species of plant in a community (3)
- set up grid with coordinates
- place large number of quadrats at random coordinates
- estimate percentage cover of native plant species
- repeat at the same time each year for many years
in northern india, there is a conflict of interests between farmers of livestock (e.g. cows) and people trying to conserve ibex (a type of wild goat)
when livestock are given extra food, their populations can grow too large and compete with ibex
name the type of competition between livestock and ibex (1)
interspecific competition
