Download Topic 5 Checkpoint Answers File

Checkpoint answers for topic 5
Q5.1 Define the term ’niche’ and produce a mind map showing how niches
affect the abundance and distribution of organisms in a habitat.
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Niche: a description of the precise role of an organism in its
environment. In simple terms, an organism’s niche is what it does and
where it lives. The niche of the chaffinch would be described in terms
of the abiotic aspects of its habitat, such as the temperature range it
can tolerate, and the biotic aspects of its habitat, such as what it feeds
on, the trees in which it nests and its competitors. No two different
species have exactly the same ecological niche.
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The way an organism
exploits (uses) its
environment/ the role
of an organism in its
community
One habitat
Occupied by single
species
many
Different
species
numerous
each has a
separate
If occupied by two species
they complete, one
succeeds and one fails
Niche
Different
feeding times
because
Abiotic factors
Biotic factors
Different food
Changing
conditions
More
favourable
conditions
Increased
reproduction
Less
favourable
conditions
Increased
emigration
Decreased
mortality
Species use
habitat in
different ways
Environmental
conditions vary
Species adapted
to conditions
survive
Increased
emigration
Different
parasites
Different
shelter sites
Determines
distribution
Increased
mortality
Decreased
reproduction
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in
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abundance
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Q5.2 Draw up a table of comparison for primary and secondary succession
and explain what is meant by deflected succession.
Primary succession
Starts in newly formed habitats where
there has never been a community
before.
The first organisms to colonise are
known as pioneer species; they will
be brought to the habitat by wind or
animals. Only those plant species that
can cope with the extreme conditions
in the new habitat will grow and
survive.
Secondary succession
Starts on bare soil where an existing
community has been cleared.
The first organisms to colonise are
known as pioneer species. Seeds of
many plant species will already be
lying dormant in the soil (as a seed
bank), and others will be brought by
the wind or animals. The species that
are best adapted to cope with the
conditions in the habitat will grow and
survive. (They are unlikely to be the
same species as would colonise in
primary succession.)
Organic material accumulates,
Conditions in the habitat change with
changing the conditions in the habitat. the growth of the pioneer species.
The development of a soil enables
seeds of small shallow-rooted plants
to establish.
As the conditions in the habitat
As the conditions in the habitat
improve, seeds from plants well
improve, seeds from plants well
suited to the new conditions can give suited to the new conditions can give
rise to adult plants. These compete
rise to adult plants. These compete
with the plants already present in the with the plants already present in the
habitat and, winning the competition,
habitat and, winning the competition,
they replace the existing plants. As
they replace the existing plants. As
the plant changes, so does the
the plant changes, so does the
associated animal community.
associated animal community.
Eventually a stable climax community Eventually a stable climax community
develops, dominated by trees. This
develops, dominated by trees. This
remains unchanged unless conditions remains unchanged unless conditions
in the habitat change.
in the habitat change.
A community that remains stable only because human activity prevents
succession from occurring is called a deflected succession. Most grassland in
the UK is prevented from reaching a climax community with trees due to
grazing or mowing. Grazing by wild animals could also deflect succession.
Q5.3 Produce a flowchart or bullet-point summary that describes the steps in
the light-dependent and light-independent reactions of photosynthesis.
The light-dependent reactions are in italics.
The light-independent reactions are in standard text.
•Energy from light raises two electrons in each chlorophyll molecule to a
higher energy level.
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•The electrons leave the excited chlorophyll molecules.
•The electrons pass along the electron transport chain in the thylakoid
membranes.
•The electrons pass from one carrier protein to the next in a series of
oxidation and reduction reactions, losing energy in the process.
•Within the thylakoid space, an enzyme catalyses the splitting of water
(photolysis) to give oxygen gas, hydrogen ions and electrons.
•These electrons from water replace those that were emitted from the
chlorophyll molecule, so it is no longer positively charged.
•The hydrogen ions from the splitting of water raise the H_ concentration
within the thylakoid.
•The energy made available as electrons pass from one carrier to the next in
the electron transport chain is used to synthesise ATP.
•The electrons which have passed along the electron transport chain combine
with the coenzyme NADP and hydrogen ions from the water to form reduced
NADP.
•Carbon dioxide combines with the 5-carbon compound ribulose bisphosphate
(RuBP).
•An unstable 6-carbon molecule forms that almost immediately breaks down
into two 3-carbon molecules: glycerate 3-phosphate (GP).
•GP is reduced to form another 3-carbon compound called glyceraldehyde-3phosphate (GALP).
•Some of the GALPs created are reduced to form carbohydrate, using ATP
and the electrons and hydrogen from the reduced NADP.
•The rest of the GALPs are used to regenerate the RuBP using the phosphate
from ATP.
Q5.4 Define the terms: habitat, population, community, ecosystem, abiotic,
biotic, autotroph, heterotroph, producer, primary consumer, secondary
consumer, predator, trophic level, decomposer.
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Habitat: the particular place where a community of organisms is found.
Woodlands, coral reefs and cultivated fields are all habitats for
particular communities of organisms.
Population: a group of individuals belonging to one species. Members
of a population are generally found in one place at a particular time and
are able to breed with one another. All the oak trees in a wood or the
frogs in a pond are examples of populations.
Community: all the living organisms found in a particular place at a
particular time. The community found on a rocky seashore, for
example, consists of all the seaweeds, together with all the different
species of animals – molluscs, fish, worms, crabs – as well as the
bacteria and single-celled organisms.
Ecosystem: all the organisms living in a particular area (i.e. the
community) as well as the non-living features of their environment.
Abiotic: an ecological factor that is part of the non-living or physical
environment of an organism. Abiotic factors include climatic features
such as rainfall and temperature; solar energy input and edaphic
factors. Edaphic factors relate to the soil.
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Biotic: an ecological factor that is part of the living environment of an
organism. Biotic factors are determined by living organisms and include
predation and competition. Biotic factors are usually density-dependent
as their effects are related to the population density of the organism
concerned.
Autotroph: an organism that builds up the organic molecules it requires
from small inorganic molecules such as carbon dioxide and water. In
order to do this a source of energy is necessary. In photoautotrophs,
the source of energy is light. In chemoautotrophs, this energy comes
from another chemical reaction. Autotrophs are producers in food
chains.
Heterotroph: an organism that gains its nutrients by feeding on other
organisms. The complex organic molecules in its food are broken down
by enzymes into simpler soluble substances before being built up again
to form the complex organic substances that the organism requires.
Heterotrophs are the
consumers in food chains.
Producer: an organism that can make its own organic compounds from
inorganic compounds either by photosynthesis or by using the energy
released from chemical reactions. Green plants, algae and some
bacteria are producers. Producers are at the start of all food chains.
Primary consumer: an organism that consumes plant material for its
food, also called a herbivore.
Secondary consumer: an organism that feeds on primary consumers;
also called a carnivore.
Predator: an organism that kills another organism before eating it. Most
familiar examples of predators, such as foxes and ladybirds, are
animals, and they usually prey on other animals. However, the term is
sometimes used to describe animals that feed on plants, and
carnivorous plants that feed on animals.
Trophic level: the position an organism occupies in a food chain, for
example as producer, primary consumer, secondary consumer or
tertiary consumer. Energy is transferred from one trophic level to the
next trophic level in a food chain. Since energy is lost to the
environment at each stage in the food chain, it is rare for food chains to
have more than five trophic levels.
Decomposer: a microorganism that lives by breaking down organic
compounds in dead material and other waste products into carbon
dioxide, water and mineral ions. Decomposers play a very important
part in the cycling of chemical elements such as carbon.
Q5.5 Write a short summary that explains how rising temperatures, changing
rainfall patterns and changes in seasonal cycles can affect plants and
animals.
There is evidence that many species that currently reach their northern limit of
distribution in, for example, southern England are shifting northwards. The
shift in distribution is a result of more successful colonisation at the northern
edge of their range. The plants are better able to survive in the more northerly
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location due to more favourable conditions. This might be because of warmer
temperatures, extended summers or changes in the pattern of rainfall. The
changing distribution of animals may be a direct response to rising
temperature, changes in rainfall patterns or the result of a shift in distribution
of the plants or animals they feed on. Higher temperatures could lead to drier
conditions which would affect distribution of species in a similar way.
Some species may become rare even though they can cope with the
changing climatic conditions because new species moving into the areas prey
on them or their food sources. If they cannot find another food source or move
to a new area they may become locally extinct. The distribution of diseases
infecting both animals and plants may also change and diseases could spread
rapidly, given a suitable climate.
Higher temperatures may lead to higher plant yields with increases in the rate
of photosynthesis up to the point where light intensity or another factor
becomes the limiting factor. But a lack of soil moisture that is likely to
accompany rising temperatures would see a decline in plant yields. This
would be particularly pronounced where crops are at the limit of their
temperature tolerance and arid conditions dominate, for example in the
tropics. It is probable that crop production in cooler temperate regions will
benefit from climate change whereas warmer tropical regions may suffer from
poorer yields.
Animals are likely to be affected where temperature acts as an environmental
cue or trigger for development or behaviour. For example, in birds and
amphibians changes in spawning, egg laying, hatching and growth rates have
been observed. For many species, the hatching of eggs or the emergence of
adults is synchronised with periods of maximum food availability. If a
mismatch occurs between hatching and peak food abundance the survival of
the species may be jeopardised if alternative food sources cannot be found.
The egg incubation temperature of some reptiles determines the sex of the
offspring. In leatherback turtles, higher temperatures in the nest result in
females. Rising temperatures could result in fewer males developing.
Q5.6 Write a summary explaining how natural selection can lead to evolution.
A population has some naturally occurring genetic variation with new alleles
created through mutations. Organisms produce more offspring than can
survive and reproduce. There is competition for survival between members of
a species. Organisms that are best adapted to conditions in their environment
are more likely to survive and reproduce. Natural selection occurs; organisms
with adaptive features that give a selective advantage survive and produce
offspring. The offspring are more likely to have any alleles that contribute to
the adaptive features, so these alleles become more common in the
population. Those organisms that are not well adapted are more likely to die
before maturity and so do not produce many offspring. Over a period of time,
the composition of the species will change to the more adapted form.
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Q5.7 Make a table for and against the production and use of biofuels for
transport. How might the following differ in their views about biofuels:
developing countries, Western countries, farmers, oil companies?
Arguments for production and use of
biofuels
Use of biofuels can reduce the use of
limited fossil fuels.
Biofuels are viewed as important
contribution to reducing carbon
emissions because they provide a
renewable energy source that is
carbon neutral.
Waste biomass such as farm waste
or food industry waste can be
recycled to produce biofuels.
Biofuels help keep the price of oil in
check and rising oil prices are now
making biofuels more cost effective
Arguments against production and
use of biofuels
Destruction of forests, wetlands and
permanent grasslands for biofuel
production releases stored carbon
into the atmosphere.
Biofuel production causes loss of
habitats and reduces biodiversity.
Food shortage can occur locally
where biofuels are replacing food
crops. Loss of land for agricultural
food crops can increase the price of
foods.
Production of biofuels requires energy
(for farming, transport and
processing) so some biofuels produce
only limited net savings in energy and
greenhouse gas emissions.
The processing may also require
large amounts of water bringing
pressure on water resources.
Some possible views for each of the groups might include the following ideas.
Developing countries may see the production of biofuels as an advantage if it
helps economic growth through increased income, employment and reduced
imports. However it may also be viewed as detrimental if the production is not
sustainable and leads to destruction of natural habitats, loss of land for food
production and forced displacement of local populations.
Western countries may see the production of biofuels as an advantage if it
provides ‘green’ energy which is carbon neutral and helps keep the price of oil
from rising as quickly. The production of use of biofuels may help these
countries meet reductions in carbon dioxide agreed at UN Climate Change
conferences. They may also see it as a disadvantage if there is expense and
resource implication in conversion of vehicles and infrastructure. There may
be concerns about environmental implications for Western countries and
developing countries.
Farmers who switch to producing biofuels may see increased profits with
production from more marginal land. However they may see disadvantages if
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it is not sustainable, due to environmental concerns such as soil erosion and
excess demands on water supply, or due to economic concerns such as
increases in the cost of food.
Oil companies may see biofuel production as a threat to fossil fuel production
reducing demand and preventing rises in oil prices. They may also see it as
an opportunity and challenge to develop new combination or efficient fuels.
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