OCR Biology F212


Key Definitions

A species is a group of individual organisms very similar in appearance, anatomy, physiology, biochemistry and genetics, whose members are able to interbreed freely to produce fertile offspring.

A habitat is the place where an organism lives.

Biodiversity is the variety of life-the range of living organisms to be found.

Species richness is the number of species present in a habitat.

Simpson's diversity index is a formula used to measure the diversity of a habitat.

Taxonomy is the study of the principles of classification.

Phylogeny is the study of the evolutionary relationships between organisms.

Biological classification is the process of sorting living things into groups.

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Key Definitions (2)

Natural classification groups things according to how closely related they are and reflects evolutionary relationships.

Prokaryotes have no nucleus.

Protocists include all the organisms that don't fit into the other four kingdoms.

Fungi are organisms that are mostly saprophytic. They consist of a mycelium with walls made from chitlin.

Plants are multicellular organisms that gain their nutrition from photosynthesis.

Animals are heterotrophic multicellular eukaryotes.

The binomial system uses two names to identify each species: the species name and the genus name.

A dichotomous key uses a series of questions with two alternative answers to help you identify a specimen.

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Key Definitions (3)

Variation is the presence of differences between individuals.

Genetic variation is caused by differences between the genes and the combinations of genes or alleles.

Continuous variation is variation in which there is a full range of intermediate phenotypes between two extremes.

Discontinuous variation is variation in which there are discrete groups of phenotypes with no or very few individuals in between.

An adaptation is a feature that enhances survival and long-term reproductive success.

Xerophytic plants are adapted to living in very dry conditions.

Species evenness is a measure of relative abundance of individuals in each species.

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Key Definitions (4)

Natural selection is 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 generation.

Speciation is the formation of a new species.

Extinction is when a species ceases to exist.

Conservation in situ means conserving a species in its normal environment.

Conservation ex situ means conserving an endangered species by activities that take place outside its normal environment.

Enivronmental Impact Assessment (EIA) is a procedure to assess the likely significant effects that a proposed development may have on the environment.

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The five kingdoms


  • have no nucleus
  • have a loop of naked DNA (not associated with histone proteins)
  • DNA not arranged in linear chromosomes
  • no membrane-bound organelles
  • smaller ribosomes than other groups
  • carry out respiration on mesosomes (special membrane systems), not mitochondria
  • smaller cells than eukaryotes
  • free-living or parasitic (some cause disease)
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The five kingdoms


  • eukaryotes
  • mostly single-celled
  • wide variety of forms
  • show various plant/animal like features
  • mostly free-living
  • autotrophic/heterotrophic nutrition
  • do not belong to any other kingdoms


  • eukaryotes
  • have a mycelium, consists of hyphae
  • have walls made of chitlin
  • multinucleate cytoplasm (has many nuclei)
  • mostly free-living and saphrophytic
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The five kingdoms


  • multicellular eukaryotes
  • cells surrounded by cellulose cell wall
  • produce multicellular embros from fertilised eggs
  • autotrophic nutrition


  • multicellular eukaryotes
  • heterotrophic nutrition
  • fertilised eggs that develop into a ball of cells called a blastula
  • usually able to move around
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The current system of classification uses eight taxa:

Domain: Eukaryotae

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Primate

Family: Hominidae

Genus: Homo

Species: sapiens

Kings Play Chess On Fine Grain Sand

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Modern Classification

Physiology is the study of how living things work (how muscles contract, how oxygen enters the blood)

Using biochemistry

A protein called cytochrome c is used in the process of respiration, samples of amino acid sequences of this protein molecule from different species can be identified and compared to see how closely they are related.

All organisms use DNA or RNA-provides the genetic code (instructions for producing proteins). Comparison of DNA sequences provides a way to classify species, the more similar the sequence, the more closely related the species.

Three domains

Bacteria (Eubacteria)

Archaea (Archaebacteria)


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Three domains

Eubacteria have:

  • different cell mebrane structure
  • different internal structure of the flagella
  • different enzymes (RNA polymerase) for building RNA
  • no proteins bound to their genetic material
  • different mechanims for DNA replication and building RNA

Archaebacteria and Eukaryotae share:

  • similar enzymes (RNA polymerase) for building RNA
  • similar mechanisms for DNA replication and building DNA
  • production of some proteins that bind to their DNA
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Random sampling means studying a small part of the habitat and assuming it contains a representative set of species that can be applied to the whole habitat.

Samples chosen at random reduces bias as researcher may be tempted to include larger or more colourful plants.

A quadrat-abundance scale/percentage cover

A point frame quadrat

A transect-Continuous/Interrupted/Line

Sampling Animals

A pitfall trap/Sweep netting/Pooter jar

Why do we sample? It can cause a temporary or permanent disturbance.

Human activities affect the environment, we can see how and reduce damage.

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Importance of identification

Before developments that affect the environment take place, an EIA must be done to assess damage.

If a rare species lives there, could have a major impact.

Early classification systems were based on observable features, appearance and anatomy, e.g. Linnaeus system

Why classify?

  • for convenience
  • make study of living things more manageable
  • easier to identify organisms
  • help see relationships between species
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Speciation can occur because of a reproductive barrier, anything that prevents effective reproduction between members of the species.

Allopatric speciation-geographical isolation prevents frree interbreeding

Sympatric speciation-biochemical change that prevents fertilisation, behavioural change such as a courtship dance that is not recognised or a physical change where the sexual organs are no longer compatible.

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Inherited/genetic variation

Environmental causes of variation

An adaptation is any variation that helps the organism survive.

Natural Selection

Darwin-Galapago's Islands Observations:

  • Offspring similar to parents
  • No two individuals identical
  • Organisms can produce lots of offpring
  • Populations then to stay fairly stable in size

Struggle to survive. Selection pressure. Better adapted individuals survive, 'survival of the fittest', pass on their characteristics. Eventually, a number of changes can create a new species.

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Evidence for Evolution

Fossil record shows:

  • Past species were different from those present today
  • Old species have died out
  • New species have arisen, often similar to older ones found in same place.

Brachiopods changed slowly over time.

Modern species of armadillo is 15cm but fossil glyptodonts were many times this size, over a metre long.

Evolution of modern horse is well documented. Evolution of humans can be seen but there are many gaps in this fossil record.

The Archaeopteryx shows features of birds and reptiles.

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Evidence for Evolution (2)

Gaps in the fossil record-fossil evidence is incomplete, only hard parts of organism survive to become fossils, so many organisms do not form fossils. Also fossils only form under certain conditions. Fossils can be destroyed after they have been formed by movements of rocks.

More recent evidence

Biological Molecules-all species arose from one original ancestor, certain molecules found throughout world-cytochrome c

Protein variation-DNA/RNA polymerase is found in all organisms. The central part of these proteins is very similar but higher organisms have added extra subunits which do not affect basic function of enzyme but improve regulation of action-different evolutionary paths a long time ago, more time for changes to accumulate.

DNA-differences in the structure of DNA can be compared, amino acid sequence.

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Evolution Today

Insects develop resistance to insecticides, e.g. malaria and DDT, concentration of insecticide in food chain

Use of antibiotics, powerful selection pressure, methicillin-resistant Staphylococcus aureus, MRSA. Medical researchers struggle to find new and effective drugs as bacterial populations rapidly become resistant to them.

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Human effects:

  • use environment to our advantage
  • dramatic rise in numbers continuing
  • using up more and more resources
  • actions harm other species, indirectly or not
  • loss of biodiversity
  • extinction may occur

Activities that reduce biodiversity/cause extinction:

  • hunting for food/over-harvesting
  • killing for protection (e.g. Anopheles mosquito or predators)
  • killing to remove competitors for food (pestcides)
  • pollution
  • habitat destruction (deforestation/clearing for development, agriculture)
  • accidental introductionof new predators/competitors
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Why do we need to conserve?

  • Economic, e.g. growth of food, fuel, timber
  • Ecological, e.g. recycling of nutrients, crop pollination, regulation of climate and atmosphere
  • (A)esthetic, e.g. pleasing natural conditions, nice to look at, experience feelings of joy or wellbeing
  • Ethical, e.g. all organisms have the right to live

Genetic diversity is important because it allows a species to evolve, without it species would not be able to adapt to environmental changes. So the following would be threats to a species with low genetic diversity:

Changes in climate.

Increased levels of pollution.

Emergence of new diseases.

Arrival of new pests.

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Former Member


Great! Thanks I printed this one out ;)

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