Topic 5 Flashcards
Define ecosystem
A system that includes all the living organisms in an area, as well as its physical environment
Define community
An interacting group of various species in a common location
Define population
A group of individuals belonging to the same species that live in the same region at the same time
Define habitat
The place where an organism normally lives
Define niche
A niche refers to the way in which an organism fits into an ecosystem
How is the number and distribution of organisms controlled within an ecosystem?
By biotic and abiotic factors
What are examples of biotic factors?
Competition- interspecific or intraspecific
Grazing, predation, disease, parasitism- relationships between two organisms, where one benefits at the other’s expense
Mutalism- relationship between two organisms, where both benefit
What are examples of abiotic factors?
Solar energy output- which affects photosynthesis in plants and behaviour in animals
Climate- includes rainfall, wind exposure, temperature
Topography- altitude, slope, aspect, drainage
Oxygen concentration
Edaphic factors- to do with soil
Pollution
Catastrophes
What are anthropogenic factors?
Factors affecting habitats arising from human actions
They can be biotic or abiotic
Why can’t two or more species inhabit exactly the same niche?
Competition for the same food/water source and shelter will mean that one species will outcompete the others by becoming the most adapted
Define succession
The process by which an ecosystem changes over time.
What’s the difference between primary and secondary succession?
Primary happens on land that has been newly formed/exposed. Secondary happens on land that has been cleared, but the soil still remains
Stages of succession
1) Abiotic factors are very harsh- only pioneer species can survive because they’re specially adapted
2) Pioneer species change the abiotic factors. When they die, they get decomposed, making basic soil
3) Conditions become less hostile, meaning that new organisms with different adaptations can move in
4) When the new organisms die and decompose, the soil becomes deeper and richer in minerals
5) The changes to the environment might make it less suitable for previous species
As succession goes on, what happens to the level of biodiversity?
It increases because the ecosystem becomes more complex
What is the final stage of succession?
The climax community, which supports the largest and most complex community of plants and animals it can
How can succession be prevented?
By human activities, like mowing, or by animal activities, like grazing
What is the equation for photosynthesis?
6CO2 + 6H2O –> C6H12O6 + 6O2
Why is light energy need for photosynthesis?
For the photolysis of water: H2O –> 2H+ + 2e- + 1/2O2
Light dependent reaction
1) Light absorption in PSII. Light energy is transferred to an electron, boosting it to a high energy level. The high-energy electron is passed to an acceptor molecule and replaced with an electron from water.
2) Light absorption in PSI. The electron reaches PSI. When light energy is absorbed by pigments, the electron is boosted to a very high energy level and transferred to an acceptor molecule.
3) NADPH formation. The high-energy electron travels down a short second leg of the electron transport chain. At the end of the chain, the electron is passed to NADP to make NADPH.
Light independent reaction
1) CO2 combines with RuBP, with the help of RUBISCO, to form an unstable six carbon compound, which breaks down immediately to form 2 GP molecules
2) 2 GP molecules are converted into 2 GALP molecules, using energy from the hydrolysis of ATP and H+ from reduced NADP
3) 1 out every 6 GALP molecules is converted into useful organic compounds
4) 5 out 6 GALP molecules are used in the regeneration of RuBP
Why does the light dependent reaction happen in the thylakoid membrane?
The enzymes needed for the reaction are here, and it absorbs lots of light
