Populations Flashcards
What is a species?
can interbreed to produce fertile offspring, and will be similar to each other while being different to other species
Why are hybrid offspring infertile?
they have an odd diploid number
Why is the phylogenic system described as a hierarchy?
it has groups contained within larger groups, with no overlap
What are organisms grouped according to?
common features and common ancestors
What is a population?
a group of organisms of the same species living in a habitat
What is a community?
all of the populations of all of the species within a particular habitat at the same time
What is species richness?
the number of different types of species in a particular area. the greater the number of species, the greater the richness
What is species evenness?
a comparison of the size of the population of different species in a particular area
What is species diversity?
a measure of how many different species are present in an area, and how many individuals of this species there are
Describe how you would collect a random sample of….?
-use a computer to generate random coordinates
-place quadrat in that random location
-collect all of ….. in the quadrat
How could you estimate the number of …. in an area?
-split areas into squares using a grid
-use a computer to randomly generate coordinates
-place quadrats in this random location
-count the number of …. in the quadrat present
-figure out the mean per quadrat
Why is it important that data is collected from random samples?
to remove bias
Why is it important to use a large number of samples?
-to ensure the sample was representative
-to produce a more reliable mean
-allows you to see anomalous results more easily
Why does biodiversity increase?
more varieties of plants
so more habitats
so more varieties of food sources
Explain when you would use different types of stats tests
chi squared- categories
t- test- means
spearman rank- correlation
What is a niche?
an organisms role within an ecosystem including their position in the food web and habitat
What is carrying capacity?
the maximum stable population size that an ecosystem can support, and it varies due to both biotic and abiotic factors
Name some abiotic factors?
temperature, light, pH, humidity
What is competitive exclusion?
when multiple species occupy exactly the same niche and one outcompetes the other to extinction
What is a fundamental niche?
the range of conditions in which an organism could survive
What is a realised niche?
the range of conditions in which an organism is actually found
What is competition?
When two or more individuals share resources that are insufficient to satisfy all requirements fully
What is intraspecific competition?
competition between individuals of the same species for resources and a mate
What does intraspecific competition determine?
the size of the population
What is interspecific competition?
competition between individuals of different species for the same resource that is in limited supply
What are the 3 possible outcomes of interspecific competition?
-one of the two species outcompetes the other (which could die out)
-both species decrease if they have equal ability to use resources
-the species are able to co-exist
What is predation?
hunting and killing for food
Explain the general predator-prey cycle
the predator lags behind the prey as it depends on it for food, and there are fewer predators than prey due to loss of energy at each trophic level of the food chain, prey peaks first
What is the lag phase?
low growth rate with low environmental resistance
What is the log phase?
growth rate at maximum, no limiting factors
When is plotting growth curves possible?
when population size grows slowly over a period of time, not when it grows rapidly over a short period of time
When are abiotic factors ideal for a species?
-ideal temperature for metabolic reactions
-not using up as much of their energy maintaining their body temperature
-more energy for growth/reproduction
-population size increases
What is an ecosystem?
a community and the non-living components of an environment
If a P value is less than 0.5…
it is statistically significant
Why is mark-release-recapture used?
for motile animals that are difficult to count
How do you do mark-release-recapture?
1- a large sample group of the animal is caught without injury
2- they are all marked as such that their survival is not affected/label is not rubbed off
3- they are released back into the same area as they were captured
4- they are allowed time to mix with the rest of the population, but not to reproduce
5- a second, unbiased sample group is captured and divided into a) ones that are marked
b) those that are unmarked
6- the population size is estimated from the equation
What is the equation to estimate the population?
population size = total individuals in first sample x total individuals in second sample / total number of marked individuals recaptured
What does the equation for mark-release-recapture assume?
-population does not change between samples (due to migration/breeding/predation)
-the marked individuals mix freely and randomly with the rest of the population
-marking does not affect the animal in any way
When would population estimation increase?
trap shy animals, more marked in recapture
What is succession?
the gradual change in an ecosystem over time in a given area due to interactions between species and the environment
How does succession happen?
-succession is the gradual change in a community over time; there are two types of succession- primary and secondary
-primary succession starts from bare rock or water and is less common nowadays
-secondary succession happens where land that has already sustained life has been drastically altered
Explain primary succession
bare rock-pioneer species that change the conditions-grass weeds take root-tree seedlings and shrubs appear
What are pioneer species?
the first species to colonise an area, and they can withstand extreme conditions. they penetrate and break through rock, and then they die and decompose- causing humus to build up and changes the environment
What is a climax community?
the final stage in succession, usually woodland
What is conservation?
the study and protection of biodiversity and natural resources
How does adding more …. increase biodiversity?
-increases biodiversity
-increases variety of habitats
-increases variety of food sources
-so biodiversity is increased
How can we ensure that samples are representative?
-random sampling to eliminate bias
-line transects to examine a change over a distance
-large number of samples
What are line transects used for?
used to estimate population size when they are unevenly distributed (like for populations that change over distance)
What is a belt transect?
when the quadrat is placed at every position along the tape measure
What is an interrupted belt transect?
when the quadrat is placed at uniform intervals along the tape measure
Explain the way primary succession works
-each new species that is able to withstand the previous environment is able to change the environment further
-each new species may change the environment so it becomes less suitable for the previous species, so the old ones get outcompeted
-as succession occurs, larger plant species and animals start to colonise the area
How do we conserve habitats?
by managing succession
Why does managing succession work?
if we maintain the earlier stages in succession, we prevent a climax community and a greater variety of habitats are conserved, hence a greater range of species
What is coppicing?
when you cut tree stems close to the ground to encourage new growth
