3.7.4 populations in ecosystems Flashcards
define population
a group of organisms of the same species occupying a particular space at a particular time ( they can potentially interbreed)
define community
all the populations of all the different species living in one habitat at the same time
define ecosystem
a community and the non- living component of its environment
define abiotic factor
non-living features of an ecosystem, such as the temperature and PH of the soil
define biotic factor
living features of an ecosystem
define habitat
place where an organism lives
define interspecific competition
competition between different organisms
define intraspecific competition
competition between the same species
define carrying capacity
an ecosystem supports a certain size of population of a species
define niche
an organisms role within an ecosystem, including their position in the food web and habitat
give examples of abiotic factors
temperature
oxygen
carbon dioxide concentration
light intensity
PH
what is the effect an abiotic factor has on a population
plants and animals become adapted to their ecosystem
these adaptations are developed through natural selection
the less harsh the abiotic factor the larger the population size
explain what interspecific competition is
members of different species are in competition for the same resource that could be in limited supply
better adapted individual is more likely to succeed
explain what intraspecific competition is
when members of the same species are in competition for resources AND a mate
briefly outline the predator- prey relationship
size of the predator and prey both fluctuate
there will always be more prey than predator
the size of the population will always change in the prey and then the predators (lag time)
in terms of niches, what is a specialist?
species with narrow niches
in terms of niches, what is a generalist?
species with broad niches
define adaptation
a feature an organism possesses that increases its chance of survival
what is the competitive exclusion principle?
two species cannot co-exist in the same habitat if they have the same niche
how does light intensity affect populations?
light intensity increases, the rate of photosynthesis increases
faster rate of photosynthesis means more plant growth
more spores and more seeds produced
extra longer photoperiod the more sunlight plants absorb
this means stomata stay open for longer and there is an increased transpiration rate
how does temperature affect populations?
cold blooded animals
- decreased temp
- less kinetic energy
- less E/S complexes formed
- reduced metabolic rate
an increased temperature means denatured enzyme
how does PH affect populations?
small change: alters charges on R groups of amino acids at active site so fewer E/S complexes formed due to induced fit
large change: h and ionic bonds break which changes the tertiary structure of the enzyme, this changes the shape of the active site meaning it is no longer complementary
how does salinity affect populations?
increased salinity = decreased water potential = increase in osmosis
H2O moves out down a water potential gradient
plasmolysis = death
how does water and humidity affect populations?
increase in humidity means a decrease in evaporation
animals: decrease in sweating and a decrease in cooling
plants: decrease in transpiration
how does the concentration of mineral ions affect populations?
fe ions : haemoglobin = o2 transport = aerobic respiration = increased ATP synthesis
nitrate ions : plants uptake amino acids + nucleotides e.g; ATP, DNA and RNA
define predation
where an organism eats another organism
suggest why ecologists may want to sample a species
- to find out what conditions a species needs for survival
- determine the effects of different treatments
- see how a range of species varies over time season
why is it not possible to count every species in a particular location?
too time consuming
what is a quadrat?
it is a sample area in a habitat marked off so organisms within it can be studied
what is systematic sampling?
sampling the area in a regular pattern e.g.; at every 3rd metre square
what is random sampling?
using a random number generator to assign coordinates to each square
why is it so important that the quadrats are placed randomly?
- avoids bias
- more representative data allowing for a valid conclusion
why is it important that a large sample is taken?
representative of the population and therefore allows for a ore accurate mean or line of best fit and provides enough data for a statistical test
explain how you would use random sampling with quadrats to estimate population sizes
- grid the area
- assign coordinates to the grid
- randomly select two coordinates
- place 1m^2 quadrat down at coordinates and then count the number of organisms/ measure percentage cover
- repeat many times and find a mean average
- calculate the area of the field
- multiply the area of the field by the mean number of organisms in 1m^2
what are transects?
a line through a habitat along which species can be sampled
what are the three types of transect?
line
belt
interrupted
what is a line transect?
a tape measure is placed along the transect and the species that touch the line are recorded
what is a belt transect?
quadrats are placed next to each other along the transect to work out species frequency and percentage cover along the transect
what are interrupted transects?
instead of investigating the whole transect of either line or belt you can take measurements at intervals
explain how you would use systematic sampling along a transect to estimate population size
- lay out a tape measure/ rope across the area of land to sample. The start of the transect should be placed at random
- place quadrats at regular intervals and count the number of organisms/ measure percentage cover
- repeat with many transects
what is mark release recapture?
how you measure an abundance of mobile organisms
what is a limitation of both quadrats and transects?
they can only record species that remain sessile (stationary)
explain how you would use mark release recapture to estimate the population size of mobile organisms
- capture a sample of a species using a trap
- count the sample
- mark the sample in non-harmful discrete way
- release them back into their habitat
- wait for a fixed period and collect a second sample
- count them and count the number that were marked from the first sample
what is the formula for calculating estimated population size?
estimated population size = total no. in sample 1 x total no. in sample 2 / number of marked animals in sample 2
mark release recapture relies on assumptions, what does it assume?
- the marked sample has had enough time and opportunity to mix back in with the population
- the marking has not affected the individuals chance of survival and the marking itself remains visible
- there is no significant changes in population size due to birth
what is the equation for chi squared test?
x2 = sum of ( O - E) ^2 / E
O= observed frequency
E = expected frequency
what is succession?
how an ecosystem changes over a period of time
why is bare rock such a hostile environment?
no soil
extreme temperatures
lack of water — dehydration
what is the name of the first species to colonise a new area?
pioneer species
what happens when a new species colonises?
abiotic factors are changed, they become more favourable
more successful competitors outcompete previous species
previous species is decomposed
forms humus and more soil
more soil means more nitrates and water retained
at the end of succession what is formed?
climax community
what are the three features of a climax community?
stable (food webs etc)
abiotic factors mostly constant
population size are stable
what is secondary succession?
happens on land that’s been cleared of all plants
what are the differences between primary succession and secondary succession?
primary :
starts with bare rock
can take thousands of years to reach climax community
there’s no soil
pioneer species needed
secondary :
starts with soil
no pioneer species needed
takes just tens of years to reach climax community
what is conservation?
the protection and management of species and habitats in a sustainable way
what does sustainability mean?
means that enough resources are taken to meet the needs of people today without reducing the ability of people in the future to meet their own needs
what are the main reasons for conservation?
ethical
economic
culture and aesthetic
what are some examples of conservation methods?
management of succession
seed banks
captive breeding
fishing quotas
protected areas
what is the name of the community by which succession is stopped artificially?
plagioclimax
exam question in chaffinches, the date of laying the first egg is determined by a number of factors. These include day length and temperature. What is the advantage to the bird of egg laying bejng determined by day length
birds do not start laying eggs when period of warm weather occurs early in the year
