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Williamwood High School
National 5 Biology
Unit 3- Life On Earth
Section 3.1 Biodiversity and the Distribution of Life
Section 3.2 Energy in the Ecosystem
Section 3.3 Sampling Techniques
Section 3.4 Adaptation, Natural Selection and the Evolution
Section 3.5 Human Impact
Student Notes___________________
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Biodiversity and the Distribution of Life– Key Areas

Biotic, abiotic and human influences are all factors that affect biodiversity in an ecosystem.

Grazing and predation are biotic factors; pH and temperature are abiotic factors.

Biomes are the various regions of our planet as distinguished by their similar climate, fauna
and flora.

Global distribution of biomes can be influenced by temperature and rainfall. An ecosystem
consists of all the organisms living in a particular area and non-living components with which
the organism interacts.

A niche is the role that an organism plays within a community. It includes the use it makes of
the resources in its ecosystem and its interactions with other organisms in the community
including competition, parasitism, predation, light, temperature and nutrient availability.
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Biomes
Ecosystems can be small-scale, covering a small area (such as a pond) or large-scale covering a large
area (such as a tropical rainforest).
The world is divided up into ten major ecosystems.
These large-scale ecosystems are called biomes.Biomes are the various regions of our planet that can
best be distinguished by their climate, fauna and flora. There are different ways of classifying biomes
but the common elements are climate, habitat, animal and plant adaptation, biodiversity and human
activity.
Biomes of the Earth
Biomes have changed many times during the history of life on Earth. Different biomes have different
effect on the planet. More recently, human activities have drastically altered these communities.
It is important to study biomes; conservation and preservation of biomes should be a major concern
to all. We must understand how human activity affects these biomes.
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Biomes – The Tropical Rainforest
In general, tropical rainforests have hot and humid climates where it
rains virtually everyday.
Rainforests now cover less than 6% of Earth's land surface. Scientists
estimate that more than half of all the world's plant and animal
species live in tropical rain forests.
Tropical rainforests produce 40% of Earth's oxygen.About 1/4 of all the medicines we use come from
rainforest plants. Quinine, from the cinchona tree, is used to treat malaria. A person with lymphocytic
leukemia has a 99% chance that the disease will go into remission because of the rosy periwinkle.
More than 1,400 varieties of tropical plants are thought to be potential cures for cancer. Biomes
containing tropical rainforests arelocated inCentral America in the Amazon river basin, African Zaire
basin, with a small area in West Africa; also in eastern Madagascar.
Biomes – Tundra
The temperatures stay below 0°C most of the year. The ground remains frozen up to 2 meters deep,
apart from a few centimetres of thaw in the summer; this makes it impossible for trees to grow.
The precipitation is gentle, mainly falling as snow. The winds can be very strong. The bare and
sometimes rocky ground can only support low growing plants like mosses, heaths, and lichen.
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When the snow and the top layer of permafrost melt, it is very soggy and the tundra is covered with
marshes, lakes, bogs and streams that breed thousands of insects and attract many migrating birds.
The tundra is not a cold and useless wasteland. It is a very fragile environment and the plants and
animals that have made their home on the tundra biome have made some incredible adaptations to
the long, cold winters and the short but abundant summers. Tundra’s can be found in North
America, Scandinavia and Russia.
Biomes – Desert
Deserts have extreme temperatures. During the day the temperature may reach 50°C, when at night
it may fall to below 0°C. Deserts have less than 250 mm of rainfall per year. The rain can be
unreliable.
Deserts are biologically rich habitats with a vast array of animals and plants that have adapted to the
harsh conditions there.
Deserts cover more than one fifth of the Earth's land, and they are found on every continent. Some of
the world's semi-arid regions are turning into desert at an alarming rate. This process, known as
"desertification," is not caused by drought, but usually arises from the demands of human
populations that settle on the semi-arid lands to grow crops and graze animals.
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Biomes – Savanna Grassland
Savanna regions have two distinct seasons - a wet season and a dry season. There is very little rain in
the dry season. In the wet season vegetation grows, including lush green grasses and wooded areas.
The Serengeti Plains of Tanzania are some of the most well known. Here, animals like lions, zebras,
elephants, and giraffes and many types of ungulates (animals with hooves) graze and hunt. Many
large grass-eating mammals (herbivores) can survive here because they can move around and eat the
plentiful grasses. There are also lots of carnivores (meat eaters) who eat them in turn.
Ecosystems
The study of organisms in their natural habitat is
called ecology.
Ecologists study animals and plants living in
ecosystems.
An ecosystem consists of a community of
organisms interacting with each other and with
their environment.
Plants and animals interact with, and are
influenced by, the non-living components of the
ecosystem such as temperature and rainfall.
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Ecosystems embody the concept that that "the whole is greater than the sum of its parts" and
"everything is connected".
Each plant or animal creates it’s own population; the number of a particular species in a given area.
All of the stickleback fish in the pond are a population of stickleback.
All of the living organisms in an ecosystem are called a community. In the pond a community is
formed from the lily pads, sticklebacks, frogs and any other living organism within that pond.
The habitat is the natural environment in which living organisms reside. The pond is the habitat.
Ecosystems – Key Term
Example – Woodland Ecosystem
Habitat: Tree
Populations: Several different populations eg
population of worms, population of woodlice.
Community: All the populations together,eg all
the woodlice, worms, birds….
Ecosystem: The community and habitat!
Biodiversity
Biodiversity is the variety of different species living in a habitat.
The greater the number of different species in a habitat, the
greater the biodiversity.
The number of species of plants, animals, and microorganisms,
the enormous diversity of genes in these species, the different
ecosystems on the planet, such as deserts, rainforests and coral
reefs are all part of a biologically diverse Earth.
Almost all cultures in some way or form recognise the importance that nature, and its biological
diversity.
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Difficulty still arises however in the appropriate balance required to preserve and maintain global
biodiversity whilst supporting human development. An additional problem for conservation bodies
trying to curb biodiversity loss is a mismatch between the conservation topics academics study and
the information conservationists need to help them preserve biodiversity.
Biodiversity in an ecosystem is affected by a variety of factors.
These factors can be classified as biotic and abiotic. Human activity
also has an impact on biodiversity.
Examples of Factors influencing Biodiversity
Biotic Factors
Abiotic Factors
Human factors
Predation
pH
Over-hunting
Grazing
Temperature
Over-grazing
Disease
Light
Deforestation
Biotic Factors
Predation
Over predation is caused by there being more predators than the
ecosystem can support.
Eventually prey will be so scarce the predators must emigrate or
starve to death.
Over predation can lead to a DECREASE in Biodiversity.
Grazing
Grazing is carried out by animals such as rabbits and sheep that
feed on a rich variety of plant species.
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By doing this they are maintaining the high diversity of an ecosystem since the vigorous grasses are
kept in check.
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High grazing therefore INCREASES biodiversity.
Low or very high grazing DECREASES biodiversity.
grazing
Disease
As the population increases, the spread of disease also increases. When the population size
increases, animals and plants live closer to each other. This makes it easier for disease to spread and
more organism die.
Disease can lead to a DECREASE in biodiversity.
Abiotic Factors
pH
The burning of fossil fuels leads to an increase in sulphur dioxide
in the environment which makes acid rain.
Acid rain has devastating consequences for biodiversity as
many plants and animal species can not survive these
conditions.
As the pH falls (more acidic), biodiversity DECREASES.
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Temperature
Organisms are adapted to the conditions in the
environment they live.
If a sudden drop or increase in temperature happens
the organism may not be able to survive and die.
Climate change threatens many species as evolution
can not keep pace with the rate at which the climate is changing.
Changes in temperature can DECREASE the biodiversity in an ecosystem.
Human Factors
Deforestation
Deforestation involves humans clearing away vast areas
of natural forest for their own benefit.
This can result in a reduction in soil fertility and poor soil
structure.
Over-hunting
Many species have been over-hunted for their skin, food
or as trophies. Regulation changes and conservation
laws go some way to stopping the impact of overhunting in some areas.
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Over-grazing
In some countries poor land management has led to soil
erosion as a result of over-grazing. Over-grazing results
in bare soil, unsuitable for growing plants. To grow food
crops forests are felled, this further exacerbates the
issue.
Niche
A niche is the role an organism plays within a community.
The above diagram shows how the honeycreeper has evolved into the modern honeycreeper species
with beak shapes which are adapted for different feeding methods.
The different honeycreepers eat different food types so have different niches. This reduces
competition for food.
Example – Niche in Woodland Ecosystem
Blue tits and squirrels both inhabit the same tree, but they do not directly compete for food: the
squirrels feed on acorns, while the blue tits feed on moth larvae.
The two species occupy different niches within the oak ecosystem.
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The ecological niche involves
both the place where an
organism lives and the roles
that an organism does in its
habitat. For example, the
ecological niche of the oak
tree includes absorbing light,
water and nutrients (for
photosynthesis), providing
shelter and food for other
organisms (e.g. bees, blue
tits, etc.), and giving off
oxygen into the atmosphere.
Success Criteria:
Traffic Light
I can state what a biome is and that it contains distinctive flora and fauna.
I can state that a biome is characterised by temperature and rainfall.
I can state that flora refers to plant life and fauna relates to animal life.
I can state what abiotic factors influence the distribution of biomes and give
examples such as temperature and pH.
I can describe named examples of biomes and give more detailed
information on the flora, fauna and biotic factors that characterise the
named biome.
I can state the definition of the terms ecosystem, population, community and
habitat.
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I can state that biodiversity is the variety of species living within an
environment
I can explain how abiotic factors, biotic factors and human influence can affect
biodiversity.
I can describe what a niche is and give an example.
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