ecosystems Flashcards
what is ecology
the study of interactions between organisms and their environment
list some physical factors that have an effect on ecology
temperature, water, sunlight, wind, soil chemistry, disturbance etc
list some biotic factors that have an effect on ecology
predator/prey, parasites, symbionts, competitors etc
what are the different levels of ecological organisation
biosphere biome ecosystem community population individual
what is the biosphere
the parts of the earth inhabited by organisms
what is the biome
a climatic region e.g. tundra, deep sea, savannah, tropical rainforest
what is an ecosystem
the functional unit of ecology: the organisms in a habitat type that interact to create its structure e.g. rainforest in the amazon catchment
what is a community
a subset of the ecosystem that is found in one location e.g. amazon rainforest birds, their prey and predators
what is a population
the members of one species that interact together e.g. macaws
give some global patterns in biodiversity
- species are not evenly distributed over the earth’s surface
- different taxonomic groups often show parallel patterns of biodiversity e.g. rainforest is a favourable environment for amphibians, mammals and birds
- distribution of threatened species is not similar for different taxonomic groups e.g. rare birds - Pakistan, rare mammals - south east Africa
- there are more species near the equator than the poles
what are the most likely explanations for the greater number of species near the equators
there is greater climatic stability and productivity at the equator, leading to greater speciation/smaller niches.
at the equator there is the same amount of daylight all year round and the climate is warmer
what happens to the mammal biodiversity when forest size is increased and why
mammal biodiversity increases - some species need a larger range than others so the increase in range allows more species to inhabit the forest
what is an island
can be an island of one habitat e.g. woodland, water
what do immigration and extinction rates depend on
island size
what does the equilibrium number of species depend on
the equilibrium number of species depends on the size of the island and the rate of immigration and extinction
compare a small island to a large island in terms of their immigration and extinction rates
immigration rate is greater in large islands compared to small islands
extinction rate is greater in small islands compared to large islands
what does McArthur and Wilson’s model of habitat locations suggest about species diversity
greater barriers to colonisation will result in lower diversity
i.e. the further away an island the less species inhabit it
what are the global patterns in body size
Bergmann’s rule - find larger bodies at higher altitudes because temperature decreases at higher altitudes - larger mammals experience less heat loss
body size is larger in regions of low biodiversity
members of a tropical species of bird are more consistent in size than members of temperate species
do all organisms need energy
yes - either form the sun, chemicals or each other
in most ecosystems how is energy form the sun converted into organic molecules
by primary producers - by photosynthesis
what is gross primary production (GPP)
the total amount of energy generated by autotrophs in an ecosystem
what is an autotroph
an organism that is able to form nutritional organic substances from simple inorganic substances such as carbon dioxide.
what is net primary productivity (NPP)
how much of the GPP is available to other organisms (autotrophs use some of the energy)
NPP = GPP - respiration by autotrophs
what fraction of GPP is usually NPP
half
in what regions of the earth is NPP greatest
equatorial regions, with high rainfall
what factors can constrain NPP
energy (temperature, light penetration of aquatic ecosystems)
water (for terrestrial ecosystems)
limiting nutrients (nitrogen or phosphorus)
what are the levels of the food chain
primary producers - plants
primary consumers - herbivores secondary consumers - carnivores
tertiary consumers - top carnivores - no predators
give an example of a food chain
oak tree leaves eaten by caterpillars, which are eaten by robins, which are eaten by sparrow hawks
what is the relationship between the levels of the food chain and their biomass
as you go up the levels of the food chain the biomass decreases
what is the effect of losing energy from at each stage in the food chain
the number of links in the food chain becomes limited - this can be demonstrated by limiting the number of leaves in a tree hole
in bottom up control what is the effect of increasing the energy or nutrient supply of the primary producers
energy or nutrient supply will increase at all levels of the food chain
what does it mean if an ecosystem is under top-down control
herbivore numbers are limited by predators, not by primary production
what is the effect of adding a top carnivore to a top down control system
it increases the number of herbivores
food webs are usually more ………….. than a food chain
complicated
what is a dominant species
are simply the most common/have biggest biomass
e.g. mussels are dominant species on a mussel bed
what are keystone species
not necessarily numerous but have pivotal role because of their niche
e.g. sea star Pisaster feeds on mussels so creates gaps for other species
how do red deer affect the hills in Scotland
they browse and prevent trees from growing, keeping the hills as moorland rather than woodland
what is bioaccumulation
increasing concentrations of pollutants and other non-metabolised molecules up the food chain e.g. DDT, PCBs, methyl mercury
what is the effect of DDT
cause egg-shell thinning in birds – but only at end of food chains, due to higher DDT concentrations - wiped out predator populations (birds of prey, pelicans, seabirds)
what are detritivores and scavengers
they mop up dead bodies and toxins can also bioaccumulate in them because they have the same diet as predators but they don’t kill the animal
many chemicals can act as ……… and enter rivers from sewage and feminise male fish
oestrogens
what are the two types of competition
- Intraspecific competition: between members of same species
- Interspecific competition: between species
why does competition arise
Arises because of resource limitations
what does the competitive exclusion principle state
if two species compete for the same resource, one will drive other to (local) extinction
what is an ecological niche
the position of a species within the ecosystem
what is the niche of a sloth
tree-top large herbivore
what is the fundamental niche
niche potentially occupied by a species – without any competition to affect the niche
what is a realised niche
niche actually occupied by that species – due to competition
what word describes coexisting
sympatry
what word describes species living separately
allopatry
what is character displacement
• A tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species - results in reduced competition
the lynx and snowshoe hare show ………. 10 year cycles
parallel
as well as influencing the numbers of prey, how else can predators affect their prey
they can influence their behaviour
e.g. zooplankton dive deeper during the day to avoid fish
describe the arms race between bats and moths
- Moths fly at night to avoid predatory birds
- Bats evolve echolocation to fly at night and feed on moths
- moths listen for bats’ echolocation clicks and either fly erratically, respond with own clicks or drop out of sky
- Some bats produce only quiet clicks when approaching a moth
what are the 2 ways that parasites can change the behaviour of their host
the host may change behaviour to avoid the parasite
parasites changes behaviour of host to increase transmission
mutualism can either be facultative or obligate what does this mean
facultative - the relationship is optional nut not essential
obligate - the relationship is essential for survival
