Paper 3 Flashcards
Define community
group of populations, living together and interacting with each other in an area
What is the law of tolerance?
The distribution of the species in an ecosystem is determined by the limits of physical and chemical factors that can be tolerated
Define keystone species
Species that has a disproportionate effect on the structure of an ecological community
Eat exerts a top down influence on lower trophic levels
Prevent lower traffic levels from monopolising critical resources
Define niche
The unique role a species plays in a community
What is a fundamental niche?
The potential mode of existence of a species, given its adaptations
What is a realised niche?
The actual mode of existence, which results from its adaptations and competition with other species
Describe the symbiotic relationship between zooxanthellae and Coral
Coral provides algae with a protected environment, and compounds they need for photosynthesis
The algae provide coral with oxygen , help with a waste removal, and supplies, coral with glucose glycerol, and amino acids
What does the competitive exclusion principle state?
No two species can occupy the same niche for extended periods of time
One species will have an advantage over the other
The less well adapted species will struggle to survive and reproduce
The less well adapted species will be eliminated
Define food chain
A linear sequence, showing feeding relationships and energy flow between species each of which feeds on the previous one
What are pyramids of energy?
Show the flow of energy between trophic levels
Measured in units of energy per unit area per unit time
Define biomass
The total dry mass of organic matter in organisms or ecosystems
What is the food conversion ratio?
A measure of an animals efficiency in converting feed mass into the desired output
Mass of food eaten divided by desired output
Define ecological succession
The predictable and orderly changes in composition of an ecosystem over time
Define primary succession
The emergence of an entirely new ecosystem
Define secondary succession
The replacement of one ecosystem by another following environmental change
Define biome
A geographical area that has particular climate and sustains a specific community of plants and animals
Define biosphere
The total of all areas were living things are found
Define climograph
A diagram which shows the relative combination of temperature and precipitation in an area
What are Gershmel diagrams?
They show the differences in nutrient flow and storage between different ecosystems
What are the sinks for nutrient storage in Gershmel diagrams?
Biomass
Litter
Soil
What are the nutrient inputs of Gershmel diagram?
Nutrients dissolved in raindrops
Nutrients from weathered rocks
What are the nutrient outputs from Gershmel diagrams?
Nutrients lost through surface run-off
Nutrients lost through leeching
What are the flows between sinks in Gershmel diagrams?
Biomass to litter is littering
Litter to soil is decomposition
Soil to biomass is plant uptake
Features of a taiga Gershmel diagram
Litter is the main store
Slow rate of nutrient transfer between stores
What is the construction of a desert Gershmel diagram?
Soil is the main store
Slow rate of nutrient transfer between stores (except for the transfer from biomass to litter)
What is the construction of the Gershmel diagram for a tropical rainforest?
Biomass is the main storage
Fast rate of nutrient transfer between stores
Define alien species
One which arrives in a non-native habitat and can become invasive
What’s the relationship between competitive exclusion an alien species
Competitive exclusion in the absence of predators can lead to reduction in the number of endemic species when alien species become invasive
Define biomagnification
A process in which chemical substances become more concentrated at each trophic level
Explain the effect of DDT
It’s a synthetic pesticide
It can be used against malaria mosquitoes
It is washed into waterways at low concentrations
It is biomagnified up the food chain
It is highly toxic at high concentrations
It reduces reproductive function
It is responsible for shell thinning in birds
Can cause cancers
What are the pros of DDT?
It is affordable and effective at killing mosquitoes that carry malaria
Alternative strategies are not successful
Health costs of treating malaria greatly reduced
What are the cons of DDT?
People exposed may suffer serious health effects
Persist in the environment for long periods of time
Define indicator species
An organism used to assess a specific environmental condition
What is the biotic index?
It compares the relative frequency of indicator species
Provides an overall environmental assessment of an ecosystem
A change in the biotic index overtime may indicate change in environmental conditions
A high biotic index indicates an abundance of pollution, sensitive organisms
A low biotic index indicates the absence of pollution, sensitive organisms
Define biodiversity
The variety of organisms present in an ecosystem
Define richness
The number of different species present
Define evenness
A habitat that has similar abundance for each species
What is the Simpsons reciprocal index?
Calculate biodiversity
Takes into account, richness and evenness
The greater the biodiversity, the higher, the value of D
The lowest possible defined value of D is one
Define in situ
The preservation of a species inside the natural habitat
Define ex situ
The preservation of species outside the natural habitats
Define species diversity
The number of species and their relative abundance
What is the area affect?
The effect of area on species richness
The larger, the geographic area, the more species, it can support
What is the edge affect?
Describes what occurs at boundaries between two habitats or ecosystems
Add edge effect increases there is greater biodiversity
What is a limiting factor?
And environmental selection, pressure that limits population growth
What are top down factors?
Pressure is applied by other organisms at higher trophic levels
Predators
What are bottom up factors?
Those that involve resources are lower trophic levels
The availability of nutrients
What is the effect of Natality on population size?
Increases to population size through reproduction
What is the effect of immigration on population?
Increases population size from external populations
What is the effect of mortality on population?
Decrease is a population size as a result of death
What is the effect of emigration on population?
Decreases to population size as a result of loss of external populations
Define a population
A group of organisms of the same species who live in the same area the same time
What is the Lincoln index?
Estimates the population of an animal species in a given area at a given time
Explain the role of bacteria in the nitrogen cycle
- bacteria decompose, the dead remains of plants
- Convert nitrogenous compounds into ammonia
- Nitrifying, bacteria, converts ammonia to nitrates
- Nitrogen fixation is the conversion of atmospheric nitrogen to ammonia
- Rhizobium have a mutualistic relationship with the plants
- Rhizobium bacteria in root, nodules of legumes, fix nitrogen
- Nitrates are absorbed by plants
- Denitrifying bacteria, convert nitrates into nitrogen gas
Impact of waterlogging on nitrogen cycle
- reduces the oxygen availability in soils
- encourages the process of denitrification
- Food crops are affected
- Leaching of nutrients
Define nutrient leaching
Leaching of minerals and nutrients from agricultural land into rivers, causes, eutrophication, and leads to increase by chemical oxygen demand
Describe the impact of run-off
- rainfall, leeches, water, soluble nutrients from the soil and carries them into rivers and lakes
- an increase in nutrients in aquatic ecosystems lead to eutrophication
- rapid growth’s in algal populations leading to algal blooms, this also increase is the number of dead algae
- number of bacteria that feeds on dead algae also increases
- an increase in via chemical, oxygen demand by the bacteria result in deoxygenation of water supply
