Genetics, Poulations, Evolution And Ecosystems (3.7) Flashcards
Ecosystems are _________, meaning they are constantly changing.
Dynamic
What happens during succession?
During succession, the biotic conditions (i.e. the living factors) and the abiotic conditions (i.e. the non-living factors) change over time
What is primary succession?
Primary succession is the process that occurs when newly formed or newly exposed land (with no species present) is gradually colonised (inhabited) by an increasing number of species
What is a pioneer species?
The first species to colonise the new land
What are 2 examples of a pioneer species?
Moss
Lichens
Describe how a climax community is formed.
Firstly, seeds and spores that are carried by the wind land on the exposed rock and begin to grow. As these pioneer species die and decompose, the dead organic matter (humus) forms a basic soil.
Seeds and spores are carried by the wind (or other ways e.g in bird faeces) and land on the basic soil and begin to grow (these smaller plants are adapted to survive in shallow, relatively nutrient-poor soils). As these small plants and shrubs die and decompose, the new soil becomes deeper and more nutrient-rich. The roots of these small plants and shrubs also form a network that helps to hold the soil in place and prevent it from being washed away.
Larger plants and shrubs, as well as small trees, that require deeper, more nutrient-rich soil, can now begin to grow.
Finally, the soil is sufficiently deep, contains enough nutrients and can hold enough water to support the growth of large trees.
What is a climax community?
The final community formed, containing all the different plant and animal species that have now colonised the new land, is known as the climax community
At each stage in succession, there are certain species that gradually _______ the local environment so that it becomes more suitable for other _________ that have not yet colonised the new land.
Change
Species
Give an example of how the new colonising species can change the environment in such a way that it becomes less suitable for the species.
As mosses grow, the basic soil continues to build up until small plants and grasses can colonise the new land. Eventually, these species result in the formation of a thin soil layer that covers the newly formed rock surface completely. As lichens cannot grow on soil, they now disappear from the ecosystem. In this way, the new species that arrived after the lichens have changed the environment in such a way that it becomes less suitable for the lichens.
What is carrying capacity?
The maximum stable population size of a species that an ecosystem can support
There are many _____ and ______ factors that prevent every individual in a population from reaching adulthood and reproducing
Biotic
Abiotic
What abiotic factors affect population size?
- light availability
- water supply
- temperature
- space available
- soil PH
What biotic factors affect population size?
- interspecific competition
- intraspecific competition
- predation
What is interspecific competition?
- competing for the same resources between individuals from different species e.g red and grey squirrels
- both populations are limited
- competition can lead to a decrease in one species and an increase in another (one is better adapted and out-competes)
What is intraspecific competition?
- competition for the same resources within the same species
- the resources become limiting and the population can no longer grow in size (carrying capacity is reached)
What is predation?
In a stable community, the numbers of predators and prey rise and fall in cycles - limiting the population sizes of both predators and prey
Describe the predator prey cycle.
- number of predators increases when more prey is available
- prey then decreases as there are new predators
- number of predators decreases as there is less prey
- prey increases as there are now fewer predators
What are the conditions for a T-test?
- the data must be continuous and normally distributed
- variances of the population must be equal
- the samples must be independent of each other
How would you conduct a T-test?
- Set H0 and H1
- Use formula to calculate T-test value (variance)
- Calculate degrees of freedom
- Extract critical value from probability table
- Reject/accept H0/H1
What is a null hypothesis?
There is no significant difference - any difference is due to chance
What is an alternative hypothesis?
There is a significant difference
Any difference is not due to chance
What is H0?
Null hypothesis
What is H1?
Alternative hypothesis
What does O stand for in the chi squared test?
Observed value
