Population size and ecosystems Flashcards
What is a fugitive species
Cannot tolerate competition. They reproduce rapidly and spread out. They are able to invade new environments rapidly
What is an equilibrium species
Control their population by competition in a stable habitat. Bacteria and rabbit populations show this type of growth
What is the birth rate
The reproductive capacity of a population; the number of new individuals derived from reproduction per unit of time
What is immigration
The movement of individuals into a population of the same species
What is a population
The number of organisms of the same species living within a given area.
What is the lag phase of a population growth chart
Population number increases very slowly because time is needed for enzyme synthesis
What is the exponential phase of a population growth chart
Plenty of nutrients and few toxic by-products so there a no limiting factors to reproduction and population size increases rapidly
What is the stationary phase of a population growth chart
Cells are reproducing but population is relatively constant as the rate of cell production = rate of cell death. The population has reached its carrying capacity because reduced resources and toxic by-products are now limiting factors
What is the death phase of a population growth chart
More cells are dying that being produced so the population decreases. Death of cells is due to lack of oxygen, nutrients or toxicity of the medium
What is the carrying capacity
the limit of a population, where the death rate is equal to the birth rate
What is a population crash
Sudden decrease in population number
What causes a population crash
When a population greatly increases its carrying capacity
What happens after a population crash
The set carrying capacity us much lower as the environment is usually damaged beyond repair
What is intraspecific competition
Competition within the same species
What is interspecific competition
Competition between different species
List factors that affect a population
Food supply Competition Predation Living space Parasitism Weather
What are biotic factors
Factors directly impacted by living things, eg. predation, disease and competition
What are abiotic factors
Factors that are not affected by living things, eg. temperature, O2/CO2 concentration, nutrient/water availability
Describe a predator-prey cycle
Predator peak is always lower than prey peak
Predator peak comes after prey peak
Occurs in a continuous cycle
What is a population index
(birth rate + immigration) - (death rate + emigration)
What are density dependant factors
Limit the carrying capacity as they weaken individuals and make them less likely to reproduce
What are density independent factors
These are not linked to the population density, eg. natural disasters
Explain mark, release recapture and tactics used to reduce its effect on the animals
Capturing an animal, marking it, and catching another load again every few hours. The way you mark them must be subtle otherwise it can inhibit their ability to catch prey or can increase their visibility an likelihood to be caught.
What is a detrivore
feed on dead and decaying matter, increase surface area for saprophytes
Why does only a little energy pass through each trophic level
some parts of the organism are inedible
some parts of the organism cannot be digested
heat energy lost via respiration
What is gross primary productivity
the energy converted in plants into organic molecules
What is net primary productivity
Plants use some of the energy in respiration, losing some as heat. The energy stored forms new biomass.
Name disadvantages of pyramids of number
due to an often large number of organisms at the bottom it is almost impossible to draw to scale
Name disadvantages of pyramids of biomass
This is very destructive as it requires killing organisms and so is generally considered unethical
What is succession
gradual change over many years where plain ground goes from being empty to being able to grow more complex life
What is a pioneer species
the first species to colonise a new area. They are usually very resistant to harsh abiotic factors
What is a climax community
the most complex environment an area can grow to
What is primary succession
the introduction of species to an area that was previously uninhabited
What is secondary succession
the reintroduction of species into a bare habitat that was previously inhabited, ie, after a forest fire
How does succession work
Each organism living there modifies the environment, usually improving soil quality and making more opportunities for other organisms to thrive
What is a niche
the role and position a species has in its environment
What are the stages of the nitrogen cycle
Deamination
Nitrification
Nitrogen Fixation
Denitrification
How do plants obtain nitrates
From the soil by active transport
Explain what happens in deamination and the product formed
Saprophytic bacteria break down dead and decaying matter. Breaking them down releases ammonia.
Nitrogen Compounds -> Ammonia
Explain what happens in nitrification and the products formed
One type of nitrifying bacteria converts ammonia into nitrites, and another converts nitrites into nitrates.
Ammonia - > Nitrites -> Nitrates
Explain what happens in nitrogen fixing and the product formed
Nodules on legume plants contain bacteria with which they have a mutualistic relationship. The bacteria make ammonia to be turned in nitrates by nitrifying bacteria.
Nitrogen -> Ammonia
Explain what happens in denitrification and the product formed
Denitrifying bacteria in the soil convert nitrates back into nitrogen gas. This works against farmers who want to keep a maximum number of nitrates in the soil.
Nitrate -> Nitrogen gas
Name the four processes in the carbon cycle
Photosynthesis
Respiration
Combustion
Decay
How is carbon removed from the atmosphere
Photosynthesis removes CO2 from the atmosphere
How is carbon returned to the atmosphere
Respiration - CO2 is a by-product of respiration
Combustion - CO2 is released from the combustion of fossil fuels
Decay - saprophytes break down organic molecules and release CO2
