population size and ecosystems Flashcards
name the things which change in an ecosystem
- species composition
- population sizes
- biological cycles
- successional changes
- energy flow
what do population numbers in an ecosystem depend on
- birth rate
- death rate
- immigration into the population
- emigration away from the population
what causes population size to increase
if birth rate + immigration rate > death rate + emigration rate
what is meant by carrying capacity
maximum population size that can be maintained over a period of time in a particular habitat/environment
give some examples of limiting factors in an environment that restrict population size
- competition for food
- disease
- predation
- competition for living space and mates
describe what is happening in the lag stage of an animal population growth curve
- takes a while to reproduce
- only a few individuals are initially present
- period of adaptation to new environment
describe what is happening in the log stage of an animal population growth curve
- resources are plentiful
- population grows at maximum rate
- no limiting factors
describe what is happening in the stationary phase of an animal population growth curve
- slows as organisms start to compete
- organisms dying in equal numbers to those produced by reproduction
- environmental resistance
- carrying capacity has been reached
describe what is happening in the death phase of an animal population growth curve
- death rate greater than rate of production
- may occur when all plants are eaten
- new diseases
describe what is happening in the lag stage of a bacterial population growth curve
- bacteria / yeast synthesising new enzymes and proteins
- rate of cell division is slow
describe what is happening in the log phase of a bacterial population growth curve
- plenty of nutrients
- cells divide at maximum rate (binary fission / budding)
- doubling in s unit time
describe what is happening in the stationary phase of a bacterial population growth curve
- cells dying at same rate they are being produced
- nutrients running out becomes a limiting factor
describe what is happening in the death phase of a bacterial population growth curve
- cell death greater than rate of production of new cells
- build up of toxic waste (ethanol/yeast, acid for bacteria)
define the term population
interbreeding group of organisms of the same species in one place at a time
define the term community
interacting population of more than one species in the same habitat
define the term ecosystem
balanced biological system where community and non-living components interact in a particular location
there’s energy flow and nutrient cycling within the ecosystem
define the term habitat
place where an organism lives
define the term niche
role of an organism within the place that it lives
define the term ecology
study of relationships between living organisms and their physical environment
define the term environment
factors in a habitat that affect an organism
define the term biotic
part of the environment that is living
define the term abiotic
part of the environment that is non-living
what is meant by a density dependent factor
effects of these factors increase as the population increases and lead to a slow down in population growth
give some examples of density dependent factors
- disease
- accumulation of toxic waste
- food availability
- predation
- space
what is meant by a density independent factor
effects of these factors do not depend on population size and all members of a population are equally affected
give some examples of density independent factors
- soil pH
- light availability
- mineral availability
- freezing / fire
- flooding
give some examples of what plants compete for
- light
- space
- water
- nutrients
give some examples of what animals compete for
- food and water
- shelter
- space
- reproductive partners
what is meant by interspecific competition
- competition between individuals of different species
why does interspecific competition occur
- two species cannot occupy the same niche in the same habitat
- the bigger the niche overlap, the more competition
what is meant by intraspecific competition
competition between animals of the same species and limits population size
what assumptions do you have to make when using the capture mark recapture technique
- no emigration or immigration
- no births or deaths
- marked individuals distribute evenly
- marking process in non toxic and doesn’t make the population more susceptible to predation
outline the process of kick sampling
- stand in river with net downstream
- kick river bottom and collect species in net
- repeat for at least 3 positions along the river
- identify each species present and number of each
outline the limitations of kick sampling
- difficult to identify all species due to similarity
- hard to count total number of each species
- may count more than once due to movement
- only gives snapshot of population - need to repeat throughout the year
what is photosynthetic efficiency
a measure of how well a plant is able to capture light energy
why is the photosynthetic efficiency percentage usually so small
- sunlight misses the leaves
- light may be reflected from leaves (green)
- only certain wavelengths absorbed by chloroplasts
- light passed through leaves (transmission)
- light absorbed by non-photosynthetic parts
define gross primary productivity
rate of production of chemical energy inorganic molecules by photosynthesis in a given area
define net primary productivity
represents the rate of production of potential food available to primary consumers
define net primary production
amount of energy in organic molecules stored in plants, which is available for herbivores or primary consumers
why is energy transfer between plants and herbivores very inefficient
- plants made of cellulose which is not easily digested
- not all of the plant is eaten eg. roots
why is energy transfer between herbivores and carnivores more efficient
- animals made of protein and fat which is more easily digested
- less energy lost in faeces
what terms are given to the trophic levels of organisms in a food chain
- producer
- primary consumer
- secondary consumer
- tertiary consumer
give three reasons why energy in plants is not passed on to the animals who eat them
- used in plant respiration
- not all of plant is eaten
- cellulose hard for animals to digest so passes through body
why is energy in animals not passed on to the predators that eat them
- lost through egestion
- undigested waste
- excretion
- metabolic waste
what is meant by succession
- change in structure and composition of species in a community over time
- species replaced by others overtime as environment changes or as a better adapted species arives
what are the different stages in a succession called
seral stages
what is meant by pioneer species
- first species to grow in new habitat
- highly adapted to harsh conditions
- lichens: able to tolerate total desiccation + low nutrients
- mosses: able to root in first soil formed by decomposing lichen, could not survive on bare rock alone
what is meant by the grassland community
- decomposing moss and lichen produce soil that the roots of low growing herbaceous plants and grasses can grow in
- seeds blown into habitat establish the grassland
- outcompete moss and lichens for sunlight
what are meant by the shrubs
- perennial woody plants that outcompete grasses and block sunlight from reaching them
- grow throughout the year and stop grasses growing underneath
what is meant by the climax community
- dominated by trees
- wide variety of plants and animals growing at variety of heights
- final stable collection of plants and animals that succession produces, which is the best adapted to the conditions
give the definition of a primary succession
habitat never before colonised, eg. bare rock
outline the gradual changes that take place during succession
- soil becomes deeper
- mineral nutrient content goes up
- biodiversity and environmental stability increase
- number of woody plants increase
- organisms live at variety of heights
- pioneer plants usually lost due to competition
give the definition of a secondary succession
series of community changes which take place on a previously colonised, but disturbed or damaged habitat
explain why a secondary succession is usually quicker than primary succession
- already existing seed bank in soil
- root systems undisturbed so plants can rapidly regenerate
- fertility and structure of soil has been substantially modified by previous organisms to make it more suitable for growth and colonization
outline how human intervention may divert the climax
- ploughing
- fire
- trampling
- poor quality soil
- grazing
- mowing
- mineral extraction and building
give the definition of facilitation
presence of an initial species that aids and increases the probability of growth of a second species
what is the significance of the pyramidal shape of a biomass pyramid
to show energy lost between each trophic level
outline what food chains do not show
- all the species at each trophic level, only one
- detritivores and decomposers which are often a greater biomass than other consumers
- omnivores or other species feeding at several trophic levels
draw an annotated diagram of the carbon cycle
s
outline the main reasons for the increase in the greenhouse effect
- the burning of fossil fuels
- deforestation
- methane increases from different sources
- CFCs
what is meant by the carbon footprint
total amount of carbon dioxide released into the atmosphere due to the actions of individuals over the course of a year
outline the consequences of global warming
- melting of polar ice caps and thermal expansion of water which could cause coastal erosion or flooding
-increased frequency of droughts and forest fires - serious effects on food production which would have economic and political connsequences
explain the process of the greenhouse effect
- radiation from sun reaches earth but some reflected back by atmosphere
- radiation that reaches earth is absorbed and re-emitted as longer wavelength radiation
- radiation absorbed by greenhouse gases which contributes to warming of the earth
what do plants need nitrogen for
- building amino acids to build proteins
- building organic bases to build nucleotides
- chlorophylls
draw and annotate a diagram of the nitrogen cycle
see poster
explain the process of nitrification and why it is so important to soil fertility
- nitrosomonas convert ammonium ions to nitrites
- nitrobacter convert nitrites to nitrates
- plant can absorb them
outline the function of azobacter and the process they are involved in
- nitrogen fixation
- free living nitrogen fixing bacteria
- absorb nitrogen from air and produce ammonium ions
- can leach into soil or used by bacteria themselves to synthesise amino acids
outline the function of rhizobium and the process they are involved in
- nitrogen fixation
- found in root nodules of legumes
- bacteria benefit by getting sucrose
- plants benefit by having amino acids produced by the bacteria
explain the advantage of legumes having root nodules
- nitrogen fixing bacteria found in root nodules produce amino acids which pass to the plant which allows them to grow in poor soils
outline the function of putrefying bacteria and fungo and the process they are involved in
- decay
- decompose proteins in dead organisms
- proteins digested to amino acids which are deaminated to produce NH2 which is reduced to produce ammonium ions
outline the function of pseudomonas and the process they are involved in
- de-nitrification
- found in boggy, waterlogged soils
- convert nitrates back to nitrogen gas so few plants can grow in these soils
outline and explain the process of eutrophication
- nitrates applied to soil and leached out as a result of rain - ending up in bodies of water
- causes an algal bloom where high levels of nutrients cause rapid growth of algae which cut off light to photosynthesising plants which die
- saprotrophic bacteria decompose the dead plants and respire aerobically using the dissolved oxygen
- this gives the water a high biological demand
- biodiversity of plants and animals in the water decreases
outline another effect of using fertilisers
reduces biodiversity by encouraging the growth of nettles and grasses which have a high demand for nitrogen, these outcompete other plants for nitrogen
outline some ways in which we can reduce problems caused by fertilisers
- restrict amount of fertiliser used
- only use fertiliser when crops are actively growing
- leave a strip of land at least 10m wide next to watercourses
- avoid leaving the land bare as it can lead to soil erosion and fertilisers go with it
outline how we can aerate soil
- ploughing increases oxygen content of soil
- installing drainage systems reduces waterlogging
- both of these encourage nitrifying bacteria and discourage denitrifying ones
give some reasons for loss of lowland raised bog habitat
- landfill development
- built development
- afforestation
