Chapter 5 - Population Size & Ecosystems. Flashcards
What is a populations size determined by?
- Birth rate (Or any other way that an organism increases their numbers).
- Death rate.
- Immigration.
- Emigration.
What are the 4 phases of a growth curve?
- Lag phase.
- Log (Exponential) phase.
- Stationary Phase (Birth rate = Death rate).
- Death phase (Birth rate < Death rate).
Why can’t the rate of increase in the log phase be maintained?
Because environmental resistance sets in.
- There is less food available.
- Concentration of waste products become increasingly toxic.
- Not enough space/nesting sites.
What is environmental resistance?
Refers to environmental factors that slow down population growth.
What are the two types of factors that will affect a population size?
Density-dependent factors and Density-independent factors.
What are examples of Density Dependent/Independent factors?
Density Dependent - Depletion of food supply, parasitism.
Density Independent - Flood, Fire.
What is an Ecosystem?
A characteristic community of interdependent species interacting with the abiotic components of their habitat.
What is the carrying capacity of a species?
The maximum population size that can be maintained over a period of time by an environment.
What is the abundance of a species?
The number of individuals in a species in a given area or volume.
How can animal/plant abundance be assessed?
- Mark-Release-Recapture.
- Kick sampling.
- Using a quadrat (Mean number of individuals/%age cover/%age frequency).
What is the most significant energy source for ecosystems?
The sun.
What is a trophic level?
A feeding level; the number of times that energy has been transferred between the sun and successive organisms along a food chain.
What is the difference between a Detritivore and a Decomposer?
Detritivore - Organisms (worms, woodlice etc.) that feed on small fragments of organic debris (Detritus).
Decomposers - Microbes (Fungi, Bacteria etc.) that obtain nutrients from dead organisms and animal waste.
What is the difference between Primary productivity and Secondary productivity?
Primary - Rate at which energy is converted by producers into biomass.
Secondary - Rate at which consumers convert the chemical energy of their food into biomass.
Why is it that about 60% of the sunlight that falls on a plant isn’t absorbed by photosynthetic pigments?
- The light may may be the wrong wavelength.
- Reflected.
- Absorbed by non-photosynthetic parts of the plant.
- Transmitted through the leaf.
What is Gross Primary Productivity?
The rate of production of chemical energy in organic molecules by photosynthesis.
What is Net Primary Productivity?
What is left of GPP after some is released by the respiration of the plant.
Why is energy lost at each trophic level of a food chain?
- Energy in molecules that are egested.
- Some energy lost as heat.
- Energy remains in molecules in parts that aren’t eaten.
Why are Carnivores more efficient at energy conversion compared to herbivores?
Carnivores food is more easily digested as they produce the correct enzymes to digest it. Herbivores need a separate gut bacteria in order to digest the cellulose cell wall in their food.
What are the problems with a pyramid of numbers?
- Doesn’t take into account size of the organism.
- Doesn’t differentiate between Juvenile and adult forms.
- Range of number may be so large, drawing to scale may be difficult.
- Pyramid may be inverted.
What Ecological Pyramid is the most accurate way of representing feeding relationships?
A pyramid of energy.
When may a pyramid of biomass be inverted?
In an aquatic ecosystem when the standing crop of phytoplankton is larger than the zooplankton.
What is the difference between primary succession and secondary succession?
Primary - Change in structure and species composition of a community over time in an area that has not been previously colonized.
Secondary - The changes follow the disturbance/damage to a colonised habitat.
What is a climax community?
A stable, self-perpetuating community that has reached equilibrium with its environment, and no further change occurs.
What is the sequence of communities, with different species and structures called? and what can it be divided up into?
Sere.
Seral stage.
What is a pioneer species?
The first species to colonise a new area in an ecological succession e.g. lichen.
What factors will affect succession?
- Migration.
- Competition.
- Inter-species relationships.
What is the difference between Inter-specific Competition and Intra-specific competition?
Inter - Competition between individuals of different species.
Intra - Competition between individuals of the same species.
What is a niche?
The role and position a species has in it’s environment, including all interactions with the biotic and abiotic factors of its environment.
What is the difference between Commensalism and Mutualism?
Commensalism - An interaction between organisms of two species from which one benefits but the other is un-affected.
Mutualism - Interaction between organisms of two species from which both derive benefit.
What human activities have caused the levels of CO2 in the atmosphere to rise?
- Burning fossil fuels.
- Deforestation.
What 3 main biological processes contribute to the Carbon cycle?
- Respiration.
- Photosynthesis.
- Decomposition.
What are the 2 ways that deforestation releases CO2 back into the atmosphere?
- Trees remove CO2 from the atmosphere through photosynthesis.
- Their burning/Decomposition releases CO2 into the atmosphere.
What is Global Warming?
The increase of average global temperature, in excess of the greenhouse effect caused by the atmosphere’s historical concentration of CO2.
What are some of the consequences of global warming?
- Melting of polar ice/
- Increased frequency of extreme weather conditions.
- Increased frequency of forest fires.
- Expansion of deserts.
- Extinction of species.
- World food production may decrease.
What is a carbon footprint?
The equivalent amount of Carbon Dioxide generated by an individual, a product or a service in a year.
How can we reduce the production of greenhouse gases?
- Recycle.
- Drive less.
- Use less air conditioning/heating.
- Reduce meat consumption (especially red).
- Avoid food waste.
- Plant trees (Afforestation).
What are the 5 main bacteria involved in the Nitrogen cycle and what do they do?
- Rhizobium (In root nodules of Legumes); Nitrogen Fixation.
- Azozotobacter (Free in soil); Nitrogen fixation.
- Nitrosomonas; Ammonium to Nitrites.
- Nitrobacter; Nitrites to Nitrates.
- Pseudomonas; Denitrifying bacteria.
What is the process that converts Detritus into Ammonium?
Ammonification.
What human activities can improve the circulation of nitrogen in agricultural soils?
- Ploughing fields.
- Draining land.
- Artificial Nitrogen fixation (e.g. Haber process).
- Using ‘brown’ manure.
- planting field of legumes and then plough back into the soil as ‘green’ manure.
What can excessive use of fertilizers cause in nearby streams?
Eutrophication - The artificial enrichment of aquatic habitats by excess nutrients, often caused by run-off fertilisers.
What measures can be taken to reduce the likelihood of eutrophication?
- Restrict the amount of fertilizer applied to the soil.
- Only apply when crops are actively growing.
- Leave at least 10m strip next to watercourses.
- Dig draining ditches.
