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3.7 Genetics, populations, evolution and ecosystems (Alevel only) - Coggle…
3.7 Genetics, populations, evolution and ecosystems (Alevel only)
INHERITANCE
POPULATIONS
EVOLUTION MAY LEAD TO SPECIATION
POPULATIONS IN ECOSYSTEMS
See folder for more details
ECOSYSTEM -
All the living (biotic) and non-living (abiotic) factors in an area and the interactions between them
They can vary in scale & in abiotic and biotic factors
Categorising Ecosystems -
Terrestrial -> Forest, Grassland, Tundra, Desert
Aquatic -> Freshwater, Marine
Carrying capacity -
An ecosystem can only support a certain size of population of a species.
Lag phase - no increase / gradual increase
Log phase - exponential increase
Stationary phase - plateau, often around carrying capacity.
Death or decline phase (sometimes) - exponential decrease.
PANDA PAW - Factors that can affect carrying capacity.
Density Dependent Factors -
Predators
Avaliability ot resources
Nutrient supply (food source)
Disease / pathogeneic spread
Accumulation of waste
Density Independent Factors -
Phenomena (eg. natural disasters)
Abiotic factors
Weather conditions
“
Density
” refers to the size of the population ie. density dependent factors are influenced by the size of a population, whereas density independent factors are not.
ECOLOGICAL NICHE
See article in folder
Fundamental niche -
The largest niche that an organism could occupy if there was no competition with other species.
Realised niche -
The portion of the fundamental niche that is occupied when competition with other organisms is taken into account - the role it actually plays in the community.
Competitive exclusion principle -
No two species can occupy the same niche at the same time. Competition exists for a particular food source or nesting position / rooting zone. There are two outcomes for this competition...
Extinction of one species
Division of resources - splitting up the niche.
NICHE -
The role that a species plays in a community. Many species share a habitat but each species has a unique niche. The niche of an organism includes...
Its habitat, food sources, use of abiotic resources, way it intereacts with same species / other species etc.
BIOTIC FACTORS -
Competition
Predation (see folder for exam Qs)
Pathogens & DIsease (bacteria, fungi, virus etc.)
SAMPLING
TEST - Random Coordinates -
(3,1) - 0
(2,1) - 3
(3,6) - 11
(3,2) - 3
(5,8) - 0
(8,1) - 1
(7,5) - 6
(8,5) - 3
(4,6) - 6
(5,5) - 3
Mean per quadrat = total / 10 = 3.6
Estimate in total area (64 unit^2) = 230.4
RANDOM SAMPLING -
Lay tapes at right angles to each other to create a grid.
Use random numbers to generate coordinates (state how)
Place the corner of a quadrat at the intersection of the coordinates
Repeat for a large number of quadrats (or until you achieve a stable running mean).
Calculate a mean and scale up to estimate the population size in the area.
TRANSECTS -
If individuals are not evenly distributed within the population, random sampling can give inaccurate data.
In ecology, transects provide a method of systematic sampling.
They are simply a line (often a tape measure) placed across the sampling area to follow the environmental gradient
eg. down a rocky shore, into a forest or down a mountain side.
LINE Transect -
Count or measure an organism that simply touches the line.
Quick technique, but some species or representative areas may be missed.
BELT Transect -
Placing a quadrat next to the line creates a larger area from which to sample.
This technique takes longer but reduces the likelihood of missing organisms.
Quadrats can be positioned one immediately after another - called a
Continuous Belt Transect
Or they can be positioned at regular intervals eg. every 2 metres - called an
Interrupted / Discontinuous Belt Transect
Transects can be repeated in parallel in order to gather repeat readings for each distance along the transect eg.
Each distance along the transect has 4 sampling repeats. A mean value can then be calculated for each distance.
SUCCESSION
Secondary Succession:
Secondary succession occurs after a natural disaster like a fire / flood.
There is already soil and there may be seeds in the soil
Secondary succession is much faster than primary succession
CONSERVATION
