3.5 Populations And Ecosystems Flashcards
what is a density dependant factor
what is a density dependant factor
Density dependent factors that affect population size are things like competition, predation and disease. The effect of the factor on the population is bigger when the population is higher.
What are density dependent factors?
Density dependent factors are biotic factors that limit the size of a population.
What do density dependent factors determine?
Density dependent factors determine the carrying capacity of a population.
What is interspecific competition?
Interspecific competition is competition between different species.
What is intraspecific competition?
Intraspecific competition is competition between members of the same species.
what is density independant factor
A density independent factor affects populations whether they are large, small or just the same.
what are some density independant factors
These tend to be abiotic factors and tend to be sudden changes to the environment such as tsunamis, volcanic eruptions and wildfires.
define ecology
The study of living things and their interactions with each other and their environment.
define ecosystems
A characteristic community of interdependent species interacting with the abiotic components of their habitat.
define populations
All the members of one species in an area that can breed with each other.
all members of one species living with one another in a habitat at the same time.
define community
All the populations of different species living togteher in a habitat
define habitat
The place in an ecosystem where an organism lives.
define niche
The role of an organism in an ecosystem, generally a feeding role
define biotic and examples
All the living and organic components of an ecosystem
define abotic and give factors
All the non-living parts of an ecosystem
what happens during lag phase
Bacteria in a nutrient broth first go through a lag phase. They are synthesising enzymes and replicating DNA. The numbers of individuals rise slowly.
what happens during log phase
As food availability is high, the growth becomes exponential. Therefore, the cells divide rapidly, reproduction exceeds death rate and the population doubles for each unit of time. This is the log phase.
whats the stationary phase
As nutrients start to run out or get depleted,
the reproduction and deaths in the population stabilise,
this is the stationary phase.
Death and reproduction are equal.
whats the death phase
Eventually the toxins in the broth build up to such an extent that deaths exceed reproduction and the population decreases in the death phase. Death could also be caused by nutrients running out in the broth.
what are the advantages random sampling
every individual organism / species must have an equal chance of being included in the sample
the sampling method ensures that the sample is representative of the whole population of each species.
This reduces subjectivity and removes bias from the data collected
define species density
SPECIES DENSITY is the number of individuals of a given species in a given area. Calculated as mean number per quadrat converted to a mean number per m2 multiplied by the area of the habitat.
whats species frequency
SPECIES FREQUENCY is a measure of the probability of finding a given species with any one placement of a quadrat in a given area. Species frequency is found by recording the presence or absence of a species in a quadrat.
What is the source of all energy in food chains?
Sunlight energy
What process do photoautotrophs use to fix carbon dioxide into organic molecules?
Photosynthesis
What do primary consumers in a food chain typically eat?
Producers (plants or photoautotrophs)
What do secondary consumers in a food chain typically eat?
Primary consumers (herbivores)
What does a food chain represent?
Energy flow through an ecosystem
In a food chain, what does the arrow head represent?
The direction of energy flow to the organism doing the eating
What is a food web?
A representation of energy flow through an ecosystem that shows complex feeding relationships
whats a producer
An organism that makes its own food
What is the first energy transfer in a food chain?
From sunlight to plants.
What is the efficiency of energy transfer from sunlight to plants?
About 0.2%.
What are some reasons not all light energy hitting a leaf can be used in photosynthesis?
Some energy is reflected, some is the wrong wavelength, and some is transmitted through the leaf.
What is the process by which plants fix carbon dioxide into organic molecules?
Photosynthesis.
What does GPP stand for in the context of photosynthesis?
Gross Primary Productivity.
How is Gross Primary Productivity (GPP) measured?
In kJ m-2 yr-1.
What is the equation that relates GPP, respiration (R), and NPP?
GPP - R = NPP.
What does NPP stand for?
Net Primary Productivity.
What do decomposers feed on?
Dead organic material.
What must the numbers on the arrows representing energy flow in a food chain do?
They must add up to what is going in.
How do you calculate efficiency in energy transfer?
Little number divided by big number x 100.
What does NPP stand for?
Net Primary Productivity
What is NPP?
The energy available to herbivores.
What happens to the energy consumed by a caterpillar from a leaf?
Some energy is not digestible and is egested as faeces.
What is the equation representing the productivity of a caterpillar?
P = C - (F + U + R)
What does ‘C’ represent in the caterpillar’s productivity equation?
The total energy consumed by the caterpillar.
What does ‘F’ represent in the caterpillar’s productivity equation?
The energy lost as faeces.
What does ‘U’ represent in the caterpillar’s productivity equation?
The energy lost as nitrogenous waste (uric acid).
What does ‘R’ represent in the caterpillar’s productivity equation?
The energy lost as heat during respiration.
What happens to the energy that is assimilated by the caterpillar?
It is used for growth, movement, and can be passed on to a secondary consumer.
What happens to uneaten leaves in an ecosystem?
They are decomposed and contribute to the nutrient cycle.
What is the significance of calculating the % efficiency of energy transfer?
It helps understand how much energy is transferred from one trophic level to another.
define succession
Succession is a change in species composition and communities over time.
What is primary succession?
Primary succession takes place on land where there has been no existing life, such as bare rock or sand dunes.
What are the stages of succession called?
The stages of succession are called seres.
What are pioneer species?
Pioneer species are the first organisms that colonize bare rock in a succession, primarily lichens.
How do lichens contribute to soil formation?
Lichens erode the rock and as they decompose, they help build up a little soil.
What organisms follow lichens in primary succession?
Mosses follow lichens in primary succession.
What is the climax community in primary succession in the UK?
The climax community is a stable end point that is typically woodland.
What happens to soil as succession proceeds?
As succession proceeds, soil gets deeper and becomes more nutrient-rich.
How does biodiversity change during primary succession?
Biodiversity increases as more plants of different types become established.
What is the final seral stage in primary succession?
The final seral stage is the climax community, which consists of trees.
What effect does competition have on biodiversity in the climax community?
The climax community may have slightly lower biodiversity due to competition for light and nutrients under the tree canopy.
What is secondary succession?
Secondary succession starts where there are seeds or spores available in the soil.
How does secondary succession differ from primary succession?
In secondary succession, soil is already established, allowing rooted plants to grow faster than in primary succession.
What events can lead to secondary succession?
Secondary succession can occur on cleared land due to construction digging, tree felling, or following a fire.
What is deflected succession?
Deflected succession is where a subclimax community is maintained usually by human interference.
How can human activities lead to deflected succession?
Human activities like grazing animals or mowing lawns prevent the establishment of shrubs and trees.
What is an example of conservation involving deflected succession?
Conservation of wildflower meadows or heather moorland can involve deflected succession.
How is heather moorland maintained at a subclimax?
Heather moorland is maintained at a subclimax by controlled burning.
What benefits does controlled burning provide for grouse in heather moorland?
Controlled burning provides ideal conditions for grouse by regenerating fresh green shoots and maintaining nesting sites.
