Topic 5- Notes Flashcards
(106 cards)
Abiotic factors:
Examples
Solar energy input (e.g. changes in a day length can be a cue for reproduction), climate, topography, oxygen concentration (v. important in aquatic systems), edaphic, pollution and catastrophes (infrequent events that disturb conditions considerably).
Biotic Factors:
Examples
Competition,(grazing, predation, disease, parasitism- one organism benefits at others expense), mutualism.
The tundra
The world’s most northerly land ecosystem.
Adaptions of the polar bear:
-Long nose with several passages, small ears, thick fur, small tail, thick layer of fat under skin, large feet covered in long hair.
What are the pioneer species:colonisation?
These are the only species that can cope with the extremes of temperature, and the lack of soil, water and nutrients.
They start to break up the rock surface-organic material accumulates- change conditions just enough for other species- wind-blown moss spores start growing.
Where does primary succession take place?
It start in newly formed habitats where there has never been a community before.
What is ecological succession?
Ecological succession is the process of change in the species structure of an ecological community over time. The time scale can be decades, or even millions of years after a mass extinction.
What happens between the pioneer phase and the climax community stage of primary succession?
Succession continues: Mosses build up more organic matter in soil, holds water. Development of soil enables seeds of small, shallow-rooted plant species that’ve reached the habitat to germinate and survive.
As conditions improve, larger, taller plant species colonise. They compete with the plant species already present in habitat & winning, they replace existing community.
Describe the events resulting or following the climax community:
Eventually, community, usually dominated by trees, is reached & this stable climax community often remains unchanged unless conditions in habitat change. Community depends on environment.
No. niches and species increases as succession continues. Climax community may have lower biodiversity than preceding succession stages as dominant species out compete others.
What are the dominant species of a community?
One that exerts an overriding influence over the rest of the plant, microbe and animal species. (Many species sharing same role are called, co-dominant). It’s often the largest and most abundant.
Where does secondary succession take place?
On bare soil where an existing community has been cleared. In most cases without human interference, secondary succession would lead to the re-establishment of a forest climax community. e.g. in ploughed field or forest fire.
Pioneer species in secondary succession:
Seeds will be lying dormant in soil, others brought by wind/ animals. Pioneer species cannot out compete slower growing species like grasses so, like Groundsel they must disperse effectively, grow rapidly, and flower quickly.
What is deflected succession?
A community that remains stable only because human activity prevents succession from running its course.
e.g. dredging a pond, sheep grazing, mowing or burning.
What is the primary productivity of an ecosystem?
The rate at which energy is incorporated into organic molecules in an ecosystem.
What are autotrophs?
Producers, organisms that can make their own organic compounds from inorganic compounds.
What are chemosynthetic autotrophs?
A primary producer that is not photosynthetic, they make organic molecules using energy released from chemical reactions.
What is the symbol equation for photosynthesis?
6CO2 + 6H2O —-(energy from light in presence of chlorophyll)—-> C6H12O6 + 6O2
How does photosynthesis work (brief overview)?
Not a single reaction- but a series catalysed by enzymes.
Light-dependent reactions- use energy from light and H from photolysis of water- produce reduced NADP, ATP +waste product O2.
Light-independent reactions- uses reduced NADP & ATP from light-dependent reactions to reduce CO2 to carbohydrates.
What is reduction (ref. to hydrogen atoms)?
Reduction can be carried out by addition of an electron on its own/ by addition of a whole H atom, consisting of a H+ ion + an electron. H+ can’t carry out reduction as they carry no electrons- but they do affect pH (increased H+ decreases pH).
Why do H2O and CO2 never come into contact?
The hydrogen, electrons and energy needed for the reduction of CO2 are transferred indirectly using reduced NADP and ATP.
Where does photosynthesis take place?
The chloroplasts. A palisade mesophyll cell in a leaf can contain as many as 50 chloroplasts. Each is made up of membranes, arranged in a very precise organised way (see diagram).
Chloroplast structure:
What are thylakoids?
A thylakoid is a membrane-bound compartment inside chloroplasts. Site of the light-dependent reactions. System of interconnected flattened fluid sacs. Proteins, incl. chlorophyll & electron carriers, are embedded in the membrane.
Chloroplast structure:
What is the thylakoid space?
Fluid within the thylakoid membrane sacs contains enzymes for photolysis.
What is photolysis?
The decomposition or separation of molecules by the action of light. In photosynthesis H2O is split.
Photo=light
Lysis=splitting
