Topic 5: Communities And Ecosystems.

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5.1.1 a) Species

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A group of organisms that can interbreed and produce fertile offspring.

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5.1.1 b) habitat

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the environment in which a speicies normally lives or the location of a living organism.

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5.1.1 c) population.

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a group of organisms of the same species who live in the same area at the same time

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5.1.1 d) community

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a group of populations living and interacting with each other in an area

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5.1.1 e) ecosystem

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a community and its abiotic environment

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5.1.1 f) ecology

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the study of relationships between living organisms and between organisms and their environment.

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5.1.2 Differences between autotorph and heterotroph

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Autotrophs are organisms that synthesize their organic molecules from simple inorganic substances whereas heterotrophs are organisms that obtain organic molecules from other organisms

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5.1.3 a) consumer

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an organisms that ingests other organic matter that is living or recently killed

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5.1.3 b) detritivore

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an organism that ingests non-living organic matter

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5.1.3 c) saprotroph

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an organism that lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing the products of digestion.

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5.1.4 What is a food chain?

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It shoes the direction of energy flow from one species to another.

EG: an arrow from A to B means that A is being eaten by B and therefore indicates the direction of the energy flow

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5.1.5 Food Web

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A diagram that shows all the feeding relationships in a community with arrows which show the direction of the energy flow.

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5.1.6 Trophic Level

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Position of organism in the food chain/ food web.
Eg: producers, primary consumers, secondary consumers and tertiary consumers.

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5.1.7 Deduce the trophic level of organisms in a food chain/food web.

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PLants/photosynthethic organisms are producers.
Primary consumers are species that eat the producers.
Secondary consumers are species that eat the primary consumers
And Tertiary consumers in turn eat the secondary consumers.

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5.1.9 What is the initial energy source for all communities?

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Light

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5.1.10 Energy flow in a food chain.

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Light energy -> producers -> (organic matter)primary consumers->secondary consumers->tertiary consumers.

between these trophic levels, energy is always lost (heat in cell respiration for detritivores and saprotrophs) occasionally the energy is also lost by digestion/excretion and death between trophic levels

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5.1.11 Energy transformations....

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are never 100% efficient

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5.1.12 What happens to the erngy and nutrients that enters/leaves ecosystems.

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Energy is not recycled. It is constantly suppled to ecosystems through light energy and flows through the trophic levels. Energy from these loses in the form of faeces,tissue loss and death is passed on to detritivores and saprotrophs.
Energy is then lost from these people through cell respiration in the form of heat.

Nutrients have to be constantly recycled. They are absorbed from the environment and then returned.

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5.1.12 What do saprotrophic bacteria and fungi (decomposers) do?

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recycle nutrients

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5.2.3 Relationship between rises in concentrations of greenhouse effect.

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The mean temperature of the earth is regulated by a steady equillibrum which exists between the energy reaching the earth from the sun and energy reflected by the earth back into space.
The incoming radiation is short wave ultraviolet and visible radiation. (some absorbed some reflected back) The radiation which is reflected back into space is infrared radiation and has longer wavelengths.
The greenhouse gases( carbon dioxide,methane, oxides of nitrogen) absorb some of these gases and re-reflect it back towards the eath.
This causes a rise in mean temperature on earth and can be disastrous.

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5.2.4 Precautionary principle.

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If the effects of a human-induced change would be very large, those responsible for the charge must prove that it will not do harm before proceeding.
This is the reverse of the normal situation, where those who are conerned about the change would have to prove that it will do harm in order to prevent such changes going ahead.

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5.2.5 Precautionary principle as justification for strong action in response to the threats posed by the enhanced greenhouse effect.

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Even though there is no proof for global warming, the strong evidence suggesting that it is linked with an increase of greenhouse gases. This should not be ignored. The is a global problem affecting everyone therefore precautionary principle should be followed. Anyone supporting th notion that we can continue to emit same amounts/more greenhouse gases should have to provide evidence that it will not cause a damaging incrrease in greenhouse effct.

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5.2.6 Consequences of global temperature on arctic ecosystems.

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-artic ice cap may dissapear as glaciers start to melt and break up into icebergs.
-permafrost will melt during summer which will increase rate of decomposition of trapped organic matter including peat and detritus which will in turn increase the release of carbon dioxide (more greenhouse effects0
-species adapted to tempt conditions will migrate north which will alter food chains and consequences on animals in higher trophic levels will increase.
-marine species may become extinct as they are sensitive to tempt changes in sea water.
-polar bears may be extinct
-pests and diseases may rise
-sea levels will rise and flood low lying areas of land
-extreme weather such as storms might become common and have disastrous effects.

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5.3.1 What increases and decreases population size

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Natality - population sized is increase as offsprings are added.
Immigration- Individuals moved into area from somewhere else hence increases population

Mortality - population decreases as some get eaten or die.
Emigration- decreases as population have moved out of area

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5.3.3 Exponential growth phase, plateu phase and the transitional phase.

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Exponential phase - Rapid increase in population growth because natality exceeds mortality rate/ abundant resources/ rare diseases and predators

Transitional phase - natality rate starts to fall as mortality rate starts to rise because of the decrease in resources and increase in predators/disease.
Population still increasing though, but at slower rate.

Plateau phase
No more population growth and the size is constant because natality rate is equal to mortality. Population has reached carry capacity of environment as limited resources and common predators/ diseases keep the population numbers constant/stable.

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5.3.4 Factors that set limits to population increase

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Shortage of resources
increase in predators and diseases/ parasites

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5.4.1 Evolution

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The cumulative change in the heritable characteristics of a population.

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5.4.2 Evidence for evolution.

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Fossils, selective breeding and homologous structures.

Fossil studies have shown that they were not identical but had similarties with existing organisms suggesting a change

Selective breeding of domesticated animals also provide evidence as they have similar characteristics to the wild ones and still breed with them. The taming of wild wolves to produce the domestic dogs we know of today. As selected wild individuals with desirable characteristics were bred and resulted in a more desirable speices

Homologous structures within species show that many bones in the limbs are common to a number of spcies and suggests that they have evolved from one common ancestor

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5.4.3 Populations tend to....

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produce more offspring that the environment can support.

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5.4.4 Why is the potential over-production of offspring result in a struggle for for survival?

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If mortality rate remains lower than natality rate than population will keep growing.

As more offspring are produced, there will be less resources. If an over-production of offspring results, the resources become scarce and individuals compete for these (results in mortality rate increases because weaker individuals wil lose out on vital resources which are essential for survival)

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5.4.5 Variation is shown in...

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members of a species

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5.4.6 How does sexual reproduction promote variation?

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It forms a new combination of alleles.
There are two stages in sexual reproduction that promote variation in a species, the first one during meiosis during when a large variety of genetically different gamates are produced by each individual.
Secon stage is fertilisation when two diff individuals are brought together to from one new one.

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5.4.7 How does natural selection lead to evolution?

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Individuals that have favourable characteristics to the environment can adapt whereas others that do not have these characteristics will not allow them to adapt.
The better adapted the individuals, the more likley they are to survive and produce offspring and eventually that unadaptable ones die out. This is called natural selection.
It results in the better adapted individuals to pass on their characteristics to more offspring as the lesser adapted ones are more likely to die before reproducing.
Over time a new generation is created with the favourable characteristics that allow them to adapt to its environment which leads evolution