SNAB- Biology Topic 5 (On The Wild Side)


how plants make food

Sunlight gives energy.

Chlorophyll- where chemicals reaction happens 

Water- Travels from roots 

Carbon dioxide- Enters the leaf through small holes on the underneath.

Carbon dioxide - sunlight = Glucose 

water- chlorophyl = Oxygen


Carbon dioxide + water = glucose + oxygen

Co2 + H20 = C6H12O6 + O2

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Oxidation and reduction 

Oxidation - addition of oxygen loss of electrons loss of hydrogen, energy is given out.

Reduction- Loss of oxygen, gains electrons, gains hydrogen, enegry take out 

Light- dependent reaction- requires light to occur.

-This takes place in the thylakoid membrane of the chloroplast. Light energy is absorbed by Photosynthetic pigments in the photo systems and are coverted into chemical enegry.

Light- Independent reaction- (Calvin cycle) Does not require light but needs some of the products of light dependent reactions.

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Non- cyclic photophosphloration (Light dependent)

1) Light enegry excites electrons, which move to higher energy levels and travel through an electron transport chain.

2) Water under goes photolysis giving an electron, replacing the electron in PSII and a protron + oxygen H2O = 2H+ + 1/2 O2

3) protrons are pulled through the thylakoid mmbrane via enegry from the electron travelling through the electron transport chain, protrons move down the concentration graident through ATP synthase. ADp + P = ATP

4) Light is absorbed by PsI, exciting an electron to move to an higher energy level. This electron is used for NADP = Reduced NADP (co-enzyme)

ATP + Reduced NADP are used in Calvin cycle - lihgt independent reaction.

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Cyclic photophosphloration

1) Light absorbed by PSI

2) Electron excites to a higher enegry level cyclic beacuse the electrons are not passed on to NADP.

3) Energy from electron transport chain pulls H+ into the thylakoid membrane to diffue through ATP synthase 


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Light independent (The Calvin Cycle)

Light indpendent stage                                                                                                                       - Does not require sunlight                                                                                                                  -Driven by an dependent on the products of light dependent stage                                                 - Takes place in the stroma of the chloroplast                                                                                    - All enzymes need for reactions are there.                                                                                        - Part of reaction when products of sugars are then stored as startch.

1) carbon dioxide is 'Fixed', combines with 5 carbon Ribulose bihosphate.

2) Unstable 6 carbon compound formed from the previous reaction into two 3-carbon compounds GP

3) ATP provides the enegry for the 3 carbon compound

4) Reduced NADP reduces the 3-carbon compound Gp is converted to GALP

5) GALP is used to regenerate Ribulose Bihosphate and some is removed from the cycle. Each turn of th cycle produces 1 net carbon that can be removed from cycle.

6) ATP is used to regenerate Ribulose Biphosphate.

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Food Chains

Energy loss in food chains- 90% of suns energy is reflected back into space by clouds and dust.

Not all wave lengths of light can be absorbed and used.

Light may not fall on chlorophyll

Limiting factors.

Calculating NPP- Net productivity= gross productivity - respiratory loss

1) some parts of organism not eaten                                                                                                    2) Eaten but cannot be digested                                                                                                         3) energy loss in excretory materials such as urine                                                                             4) Energy losses occur as heat from prepration and movement 

Enerhy transfer = Enegry avalible after the tranfer/ energy avaliable before tranfer 

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Ecosystem- All organisms and non-living factors in a particular area

Habitat- Place where organisms live 

Population- All organisms of one species in a habitat 

Distribution- Where a species is in a particular area

Niche- Role and postition a species has it environment 

Microhabitat- Localized, small-scale environment, Tree stump, dead animals 

Interspecific competition : Indiviuals of diffrent species compete for some resource

Intraspecific competiton: Same species compete for limited resorces. Leading to reduction in fitness.

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Factors affecting Distribution

ABIOTIC- Non-living, chemical and physical factors in the environment which affect an ecosystem.

Water, light, wind, soil, humidity, minerals, gases, topograhy. Affect ability of organisms to survive,reproduce: restrict growth.

Biotic: Living compounds; plants and animals All- living things- autotrophs and heterophs- plants, animals, fungi, bacteria 

Living things that directly or indirectly affect organisms in the environment, organisms, interactions, waste, parasitism, disease, preditation

Both Abiotic + Biotic factors affects individual species population, community, ecosystem.

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Sampling Techniques

Random- removes bias   Repeated- Reliable/ validity  

 Estimated whole area - save time and save money.

Pitfall trap- Steep hole with food at the bottom to entise organisms in and can not climb out.

Pooter- **** the tube to pull the inscect into a clear tube.

Sweep net- used to capture air born insects, this is used in trees, air, forests.

Dipping net- To capture animals in the water.

Estimated population size = Number of individuals in first sample X Number of individuals in second sample / Number of marked individuals recaptured.

Animals must be marked in a way in which it will not harm or put the individual at harm.

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Sampling Techniques

Quadrats - are placed randomly

These only work for immobile such as plants, the more data collected the more reproducable the results are.

This method is a frame quadrat, it is ideal for quickly investigating an area. The percentage cover can be calculated. 

A point quadrat- % cover = Number of hits/ Total number of pins X 100

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A community consists of all plants and animals that occupy a particular area.

Individual populations in a community interact with each other.

A community is a constantly and dynamic unit, this passes through a number of stages from Orign to Climax

Transtion from one stage to the next is called succession.

Primary succession (No Soil) (newly formed or exposed land)

Pioneer species - Well adapted and will begin to change the abiotic conditions making the land less hostile.

Secondary succession- (soil) (land has been cleared of plants but soil remains). Pioneer species tend to be larger at this stage.

Climax Community- Climax species are now beiwng fully supported by the habitat.

Defected succession (Plagloclimax) when succession is stopped artifically Usually by humans.

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Evidence for change in climate

Dendrochronology- Tree rings to show and analyze atmospheric conditions and age of the tree. Rings are thicker is the tempture is higher. If the rings are thinner the tempture is lower. 

Tempture higher - Tree rings are thicker, growth of the tree is quicker.

Tempture lower- Tree rings are tinner, meaning growth of tree is quicker.

Pollen in Peat Bogs- Pollen is preserved/ builds up.

Pollen comes from mature plants (successfull), This can be used to show the tempature chnage over thousand of years.

Evidence from ice cores can help show tempture change. Ice contains information about temperature and gases within the atmosphere, this shoes us how it has changed over many years.

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Causes of global warming

Benefits of natrual greenhouse effects.

Natrual greenhouses effects mae sure that earths tempture remians constant to keep the earth warm and able to substain lide in order for enzymes to work and able for them to grow. If greenhouse gases were not avaliable earth would be cold and would be unable to substain life.

Greenhouse effect and global warming.

Enhanced greenhouse effect are added to the natrual gases, this is dangerous as these cases trap large amounts of heat, as there are more of these gases being released they are becoming trapped increasing global warming.

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Evolution, Natural selection and speciation

Evolution is when the frequwncy of an allele in a population chnages over time. This occurs by natural selection.

1) Individuals within a population vary because they have diffrent alles, this is due to gene mutations. (A change in a DNA base sequence).

2) Meaning some individuals are better adapted to their environment than others.

3) individuals that have an allele that increases their chance of survival are more likely to survive, reproduce and pass on theor genes.

Isolation reduces Gene flow leading to speciation

Species- Is a group of similar organisms that can reproduce to give fertile offspring and speciation is the development of a new speices.

Speciation happens when populations of the same species become reproductively isilated, reducing gene flow between two popoulations this means that natural selection acts on each popullation separately- so new species can develop.

Reproductive isolation may occur because of geographical isolation or because of random mutations produce chnages in phenotype that prevent populations from mating.

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Evolution, Natural selection and speciation

Allopatric speciation requires geographical isiolation

1) Populations that are geographically sseparated will experience slighly different conditions (Different climate)

2) The populations will experience different selection pressures so different chnages in allele frequencies could occur. - Different alles will be more adventageousin different poptlations such as a cold climate than before longer fur will be beneficial, natrual selection will then act on allels for fur length in this population, increasing the frequency.

- Allele frequencies will also change as mutations occur independently in each population.

3) Changes in allele frequency will lead to differences growing in the gene pools of the seperated populations, causing chnages in phenotype frequenices.

4) Different populations will become genetically distinct. Individuals from the different populations will have chnaged so much they wont be able to breed with another to produce fertile offspring, they will have become reproductively isolated. The two groups have become seperate species.

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Evolution, Natural selection and speciation

Reproductive isolation occurs because the changes in alleles and phenotypes of the two populations prevent them from successfully breeding together.

- Seansonal chnages: indviduals from the same population develop different flowering or mating seasons, or become sexually active at different times of the year.

-Mechanical changes: changes in genitalia prevents successful mating.

- Behacioual changes: a group of individuals develop courtship rituals that arnt attractive to the main population.

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Evolution, Natural selection and speciation

Speciation without geographical isolation is called sympatric speciation.

- Most eukaryotic organisms are diploid- they have two sets of homologous chromosomes in theor cells. Sometimes mutations can occur that increase the number of chromosomes (Polyploidy)

- Individuals with different numbers of chromosomes cant reproduce sexually to give fertile offspring. so if a polyploid organism emerges in a diploid population the polyploid organims will be reproductively isolated from the diploid organisms.

-If the polyploid organism reproduces asexually a new species could be developed.

- More common in plants.

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