Topic 5- Notes Flashcards
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
Chloroplast structure:
What is the DNA loop?
Chloroplasts contain genes for some of their proteins.
Chloroplast structure:
What is the stroma?
The fluid surrounding the thylakoid membranes. Contains all the enzymes needed to carry out the light-independent reactions of photosynthesis.
Chloroplast structure:
What are starch grains?
Stores the product of photosynthesis.
Chloroplast structure:
What is the granum?
A stack of thylakoids joined to one another. Grana (plural) resemble stacks of coins.
Chloroplast structure:
Describe the outer membrane:
Freely permeable to molecules such as CO2 and H2O.
Chloroplast structure:
Describe the inner membrane:
Contains many transporter molecules. These are membrane proteins which regulate the passage of substances in and out of the chloroplast. These substances include sugars and proteins synthesised in the cytoplasm of the cell but used within the chloroplast. The inner and outer chloroplast membrane form an envelope.
Why does photosynthesis take place inside chloroplasts?
1-Thylakoids and the light-dependent reaction:
Photosynthesis- enzyme controlled reactions- some energy stored as chem. potential energy within ATP in H2O. ATP forms in light-d reactions- due to many Ox and De-ox reactions- involve transfer of electrons between electron carrier molecules- located in thylakoid membranes- creating an electron transport chain- allows electrons to pass from one e- carrier to next.
Why does photosynthesis take place inside chloroplasts?
2-The stroma and the light-independent reaction:
ATP acts as energy carrier within cells allowing small amounts of energy to be transferred and used when needed. Chem. potential energy in ATP used as fixing CO2 to form organic molecules-reactions dependent on collision and appropriate enzyme to catalyse the reactions.
The stroma compartmentalise the reactions to allow for them to be catalysed quickly, without having too high conc. of each enzyme- which would be v. costly in term of synthesis of enzymes or too low- which would reduce rate of reaction and efficiency of photosynthesis.
The light-dependent reactions:
- Light absorbed by PSI & PSII.
- Light energy increases energy of 2 e- in each chlorophyll-‘excited’.
- e- leave chlorophyll and pass along a series of e- carrier molecules- molecules form the e- transport chain
- e-‘s from PSII chlorophyll loses energy as going from one carrier to next in many ox/ de-ox reactions. Energy used in synthesis of ATP- process called photophosphorylation.
- e-‘s from PSII replace those lost from the PSI chlorophyll.
- e-‘s lost from PSII chlorophyll replaced to continue flow of e-‘s along e- transport chain.
- In thylakoid space, enzyme catalyses splitting of H2O giving O2 gas, H+ & e-‘s- replacing those emitted from PSII chlorophyll molecule- no longer +vely charged, H+ conc. increases in thylakoid space because of photolysis.
- e-‘s from PSI chlorophyll that’ve passed along e- transport chain combine w/ the co-enzyme NADP & H+ from the H2O to form NADP.
What is ATP?
Adenosine triphosphate-most important energy transfer molecule within cells. A nucleotide-adenine, ribose and a 3 phosphate group. Moves energy around cell from energy-yielding reactions to energy-requiring reactions.
How does ATP make ADP?
3rd phosphate loosely bonded to 2nd so removed easily. When this phosphate group removed from ATP, adenosine diphosphate (ADP) forms. When removed phosphate group becomes hydrated- bonds form around H2O. Energy released as bonds form between H2O & phosphate group- used to drive energy-requiring reactions in cell. ATPase catalyses breakdown of ATP to ADP.
What is the equation linking ATP and ADP?
ATP in water —-> ADP+ hydrated Pi+ energy.
Making ATP…continuing…:
ATP produced from ADP by +ing inorganic phosphate (Pi). Addition of phosphate to ADP called PHOSPHORYLATION. To make ATP phosphate must separate from H2O- requires energy. ATP in H2O is higher energy than ADP & phosphate ions in H2O-ATP is a way of storing chemical potential energy. ATP formation separates phosphate and water. Phosphate and water brought together in an energy-yielding reaction each time energy is needed for reactions within the cell- ATP transfers energy around the cell.
Where does the light-independent reaction of photosynthesis take place?
In the stroma of the chloroplasts using the reduced NADP and ATP from the light-dependent reactions.
What is carbon fixation?
In the Calvin cycle, the inorganic carbon in CO2 is incorporated into organic molecules, initially glycerate 3-phosphate (GP).
The carbon is fixed in organic molecules making it available to other organisms.
What happens during the Calvin cycle in the Light-independent reactions?
1) CO2 combines w/ 5-C compound (ribulose biphosphate- RuBP)-reaction is catalysed by enzyme ribulose bisphosphate carboxylase (RuBISCO)-most abundant enzyme in the world.
2) The 6-C compound formed is unstable, breaks down immediately into 2 3-C molecules, glycerate 3-phosphate (GP).
3) 3-C compound reduced to form 3-C sugar phosphate called glyceraldehyde 3-phosphate (GALP). H for reduction comes from the reduced NADP. ATP provides energy for this endothermic reaction.
4) 2 out of every 12 GALPs formed are involved in the creation of a 6-C sugar (hexose) which can be converted to other organic compounds, e.g. amino acids or lipids.
5) 10 out of every 12 GALPs are involved in the recreation of RuBP. The 10 GALP molecules rearrange to form 6 5-C compounds which are then phosphorylated using ATP to form RuBP.
Where is the glucose produced from the Calvin cycle used?
- Plants in respiration.
- To make sucrose-transported around plant via phloem.
- Polymerised forming polysaccharides starch & cellulose.
- Production of lipids, amino acids (proteins) and nucleic acids.
What are primary consumers?
Herbivores- heterotrophs that eat plant material.
