Populations and ecosystems Flashcards
Define ecology
study of inter-relationships between organisms and their environment
Define the term abiotic factor
Non living factors in an environment eg temperature or rainfall
Define the term biotic factor
living factors in an environment eg competition and predation
Define ecosystem
dynamic system made up of a community and all of the non living factors of its environment
Name two major process that occur within an ecosystem
flow of energy
cycling of elements
Define population
group of individuals of the same species occupying the same habitat at the same time and can interbreed
Define community
the populations of different species in a particular place at the same time
Define habitat
the place where an organism normally lives
Define microhabitat
a smaller unit within a habitat with its own microclimate
Define niche
how an organism fits into its environment (where the organism lives and what it does there)
Why do we describe populations as dynamic?
they vary in size and composition over time
Why is it necessary to use a logarithmic scale to plot growth curves for rapidly reproducing organisms?
So that all of the data can be represented on the same axis
Define limiting factor
factor that limits the growth of a population
State the factors that affect the size of a population
abiotic and biotic factors affect rate of growth and size of a population
Define carrying capacity
the size of population of a species that can be supported by the ecosystem
Describe how temperature affects a population size
different species have different optimum temperatures. Temperatures above or below these may slow/denature enzymes in cold blooded animals or require excessive energy use to maintain in warm blooded animals
Describe how light affects population size
Light is required for photosynthesis. More light, more photosynthesis, more biomass both for plant survival and for animals to feed on
Describe how pH affects population size
pH affects action of enzymes. Organisms have an optimum pH and will not survive well in pH away from optimum
Describe how water affects population size
In scarce water conditions only well adapted organisms survive.
Describe how humidity affects population size
in low humidity transpiration and water loss increase. Plants and animals well adapted to tolerate low humidity will have larger population size
Why is it necessary to use a logarithmic scale to plot growth curves for rapidly reproducing organisms?
So that all of the data can be represented on the same axis
Describe competition
when 2 or more species share a resource that is insufficient to satisfy their requirements fully
Describe intraspecific competition
competition between members of the same species
Describe interspecific competition
competition between individuals of different species
Outline how the availability of resources affects a population
less resources - more competition - lower population size
Explain how competition causes smaller numbers of large trees in a forest rather than larger numbers of small trees
trees compete for resources - a few grow larger -this restricts resources for the others - which die
How does interspecific competition affect population size?
the population with the competitive advantage will increase in size while the other will decrease.
What is the competitive exclusion principle?
one species has the competitive advantage over another - population of less competitive species will decrease - until it becomes extinct
Describe the competitive exclusion principle in terms of niches
when resources are limiting no two species can occupy the same niche
Suggest how an increased food supply may result in a population increase
More food - more individuals survive - increased reproduction - increase in population
Define predator
organism that eats another organism
Define prey
organism that is eaten by another organism
Comment on the evolution of predators and their prey if extinction has not occurred
predators evolved to be more effective at catching prey - prey evolved simultaneously to be more effective at avoiding predators
Explain why it is difficult to obtain data on predator and prey populations in natural environments
it is not possible to count all individuals
Describe the predator prey relationship
predator eats prey and reduces prey population - fewer prey means greater competition for food amongst predators - predator population decreases due to lack of food - less predators so less prey eaten and more survive and reproduce - prey population increases - repeat
Suggest why fluctuations in natural predator prey populations is not generally severe
a range of food is available to the predators
Why is sampling done in ecology?
To find the abundance of organisms in an area when it is not possible to count every one individually, too time-consuming and is likely to cause damage.
