OCR Biology F212 Module 3 Biodiversity & Evolution

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Unit F212: Molecules, Biodiversity, Food & Health Module 3: Biodiversity & Evolution
2.3.1 Biodiversity
Biodiversity: The number and variety of organisms found within a specified ecosystem or
biome.
Species: A group of living organisms consisting of similar individuals capable of exchanging
genes or interbreeding. The principal natural taxonomic unit.
Habitat: The natural home or environment of an animal, plant, or other organism.
Levels of biodiversity
Habitat (ecosystem) diversity
The variety of habitats/ecosystems present in a biosphere.
Species diversity
The effective number of different species that are represented in a
collection of individuals (a dataset). Species diversity consists of two
components - species richness and species evenness.
Genetic diversity
The total number of genetic characteristics in the genetic makeup of a
species. It serves as a way for populations to adapt to changing
environments.
Sampling
Importance of Sampling
Human activities affect the environment, and we must study these
effects to understand the impact we have. EIAs are important parts of
planning processes and are used to estimate the environmental
effects of a planned development.
Measuring Biodiversity
To measure the biodiversity of a habitat, all the individuals of all of the
species must be counted. This is impractical, so instead, the habitat is
randomly sampled ­ random portions of the habitat are selected and
studied in detail. An estimation of the numbers in the whole habitat is
then calculated. These methods must be standardised.
Sampling Plants:
Ways to randomly select areas:
o Taking samples at regular distances across the habitat
o Using random numbers to plot coordinates within the
habitat
o Selecting coordinates from a map and then using a GPS
to find the position inside the habitat
Method 1: Random Quadrats
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Unit F212: Molecules, Biodiversity, Food & Health Module 3: Biodiversity & Evolution
o Quadrat is placed at random on the habitat and the
plants within the quadrat are identified.
o Abundance is then measured in one of three ways:
Abundance scale ­ Each species in the quadrat
has an abundance score applied to it - ACFOR.
Percentage cover ­ The percentage cover of
each plant in the quadrat is estimated.…read more

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Unit F212: Molecules, Biodiversity, Food & Health Module 3: Biodiversity & Evolution
Species Richness & Evenness
Species richness: The number of species found in a sample area
Species evenness: How evenly distributed the number of individuals are between the
numbers of species present
Estimating richness
A qualitative survey can be used, i.e. the various sampling methods.
They more species present, the richer the habitat.
Estimating evenness
This is more difficult, and a quantitative survey must be used.
Plants:
Area must be sampled.…read more

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Unit F212: Molecules, Biodiversity, Food & Health Module 3: Biodiversity & Evolution
High SID values indicate a diverse habitat ­ small change may affect one species, habitat
therefore able to withstand change, it is stable;
Low SID values suggest habitat dominated by a few species ­ small change could
damage/destroy whole habitat.
Current Estimates
It is estimated that there is about 2,000,000 species in the world, and about 100,000 in the
UK (these figures do not include marine species).…read more

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Unit F212: Molecules, Biodiversity, Food & Health Module 3: Biodiversity & Evolution
Mostly free living
Have autotrophic or heterotrophic nutrition
Fungi ­
Eukaryotes
Have mycelium which consists of hyphae
Walls made of chitin
Cytoplasm is multinucleate
Mostly free living and saprophytic
Plantae ­
Eukaryotes
Multicellular
Cells surrounded by a cellulose cell wall
Produce multicellular embryos from fertilised eggs
Autotrophic nutrition
Animalia ­
Eukaryotes
Multicellular
Heterotrophic nutrition
Have fertilised eggs that develop into balls of cells called blastula
Usually able to move around
Taxonomic Classification
Organisms…read more

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Unit F212: Molecules, Biodiversity, Food & Health Module 3: Biodiversity & Evolution
Organisms are named using the binomial system - using two names: the genus name and
the species name, e.g. Homo sapien, which can be abbreviated to H. sapien. It is always
italicised (underlined when handwritten), and the genus is always capitalised.…read more

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Unit F212: Molecules, Biodiversity, Food & Health Module 3: Biodiversity & Evolution
Flagella with a different internal structure
Different enzymes for building RNA
No proteins bound to their genetic material
Different mechanisms for DNA replication and building RNA
Archea share certain features with the Eukaryotae:
Similar enzymes for building RNA
Similar mechanisms for DNA replication and building RNA
Production of some proteins that bind to their DNA
This system of Domains is commonly accepted and is above Kingdoms (see Taxonomic
Classification).
2.3.…read more

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Unit F212: Molecules, Biodiversity, Food & Health Module 3: Biodiversity & Evolution
Genetic Variation: Our genes define our characteristics - we inherit a
unique combination of alleles from our parents. We may share many
alleles and genes with others in our species; however as there are
approx. 25,000 genes (many with multiple alleles), there is a very
remote chance of any two individuals having the same combination
(except identical twins).
Environmental Variation: Many characteristics can be environmentally
affected, e.g.…read more

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Unit F212: Molecules, Biodiversity, Food & Health Module 3: Biodiversity & Evolution
Over time, a number of changes may give rise to a new species
Natural Selection: The `selection' by the environment of particular individuals that show
certain variations. These individuals will survive to reproduce and pass on their variations to
the next generations.
We say that individuals undergo selection pressure if they have beneficial characteristics for
the species.…read more

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Unit F212: Molecules, Biodiversity, Food & Health Module 3: Biodiversity & Evolution
The problem with fossil evidence is that it's incomplete. Usually only
the hard parts of an organism become fossilised and not all organisms
have hard parts. Fossils also only form under certain conditions.
Molecular Evidence
If one species gives rise to another, both are likely to have the same
biological molecules. This suggests that all species arose from one
original ancestor - monogenism.…read more

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