Biodiversity and evolution



  • A species is a group of individual organisms very similar in appearance, anatomy, physiology, biochemistry and genetics, whose members are able to interbreed freely and produce fertile offspring.
  • habitat is the place where an organism lives.

Organisms are oftern very well adapted to their habitat, especially if the conditions are extreme. E.g. woodland, freashwater ponds and rockpools.

  • Biodiversity is the number and variety of living things to be found in the world, in an ecosystem or in a habitat.

Can be considered at a number of levels such as the range of habitats in which different species live, the differences between species and genetic variation between individuals belonging to the same species.

  • An ecosystem is all the living organisms and non-living components in a specific area and their interactions.
  • niche is the exact role of an organism in the ecosystem.
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Measuring biodiversity

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

You can use a qualitative survey to estimate species richness. You need to make observations within the habitat and record all the different species you see. Method of sampling will depend on the habitat.

  • Species eveness is the number of individuals there are of each species in a habitat.

A quantitve survey must be used. You would be required to count the number of each species per unit area (E.g. large plants, larger animals), or measure the percentage cover of each species (E.g. grass, small animals) for animals the mark-and-recapture technique is required.

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

Takes into account both species eveness and species richness.

A high value indicates a diverse habitat, such a habitat provides a place for many different species and many organisms to live. A small change to the enviroment may affect one species, therefore the effect on the whole habitat is small. The habitat tends to be stable and able to withstand change.

A low value indicates a habitat dominated by a few species, in this case a small change to the enviroment that effects one of those species could damage or destroy the whole habitat.

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Classification and taxonomy

  • Classification is the organisation of living organsims into groups according to their shared similarities.
  • Taxonomy is the study of the principles of clssification,

The study of differences between species.

  • Phylogeny the study of the evolutionar relationships between organisms.

The study of how closely related different species are. The closer two species are related, the closer they appear on the evolutionary tree. Also more recently in the pass they shared a common ancestor.

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  • Prokaryotes are organisms that have no nucleus.


  • Have no nucleus.
  • Have a loop of naked DNA that is not arranged in linear chromosomes.
  • Have no membrane-bound organelles.
  • Have smaller ribosomes than in other groups.
  • Carry out respiration not in mitochondria, but on special membrane systems called mesosomes.
  • Have cells smaller than those of eukaryotes.
  • May be free-living or parasitic.

Kingdom Prokaryota

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  • Protoctists include all the organisms that don't fit into the other four kingdoms. Many are single-celled, but some are multicellular.


  • Are eukaryotes.
  • Are mostly single-celled.
  • Show a wide variety of forms.
  • Show plant-like or animal-like feautures.
  • Are mostly free-living.
  • Have autotrophic or heterotrophic nutrition.

The only thing all protoctists have in common is that they don't qualify to belong to any of the other kingdoms.

Kingdom Protocista

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  • Fungi are organisms that are mostly saprophytic. The consist of a mycelium with walls made from chitin.


  • Are eukaryotes.
  • Have a mycelium which consists of hyphae.
  • Have walls made of chitin.
  • Have cytoplasm that is multinucleate.
  • Are mostly free-living and saprophytic - cause decay of organic matter.

Kingdom Fungi

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  • Plants are multicellular organisms that gain their nutrition through photosynthesis.


  • Are eukaryotes.
  • Are multicellular.
  • Have cells surrounded by a cellulose cell wall.
  • Produce multicellular embryos from fertilised eggs.
  • Have autotrophic nutrition.

Kingdom Plantae

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  • Animals are heterotrophic multicellular eukaryotes.


  • Are eukaryotes.
  • Are multicellular.
  • Have heterotrophic nutrition.
  • Have fertilised eggs that develop into a ball of cells called a blastula.
  • Are usually able to move around.

Kingdom Animalia

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Classification systems

  • Domain Did
  • Kingdom King
  • Phylum Philip
  • Class Come
  • Order Over
  • Family For
  • Genus Good
  • Species Soup
  • The binomial system uses two names to identify each species: the genus name and the species name.
  • dichotomous key uses a series of questions with two alternative answers to help you identify a specimen.

Cytochrome c is present in all respiring organisms. The amino acids in cytochrome c can be identified and compaired. If two sequences are the same the two species must be closely related. If the sequences are different the species aren't closely related, the more differences found between the sequences the less closely related the species are.

Comparison of DNA sequences provides a way to clearly classify species. The more similar the sequence the more closely related the two species.

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

Variation occurs within and between species.

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

E.g. Height in  humans, lenght or reproductive hypha of a toadstool, length if leaves on an oak tree.

  • Discontiuous variation is variation between living organisms in a species in which there are discrete groups of phenotypes with no or very few individuals in between.

E.g. Sex, presence of flagella in bacteria, human blood groups

Varitation can be inherited or influenced by the enviroment. Genes we in herit provide information that is used to define our characteristics however they can be affected by the enviroment. Good diet leads to increased height but height is limited by genes.

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  • An adaptation is a feature of a living organism that increases its chances of survial and long-term reproductive success.

Adaptations help the organism cope with enviromental stresses and obtain thng they need to survive. Adaptations can work in different ways.

Behavioural adaptations are an aspect of the behaviour of an organism that helps it to survive the conditions it lives in. When touched an earthworm quickly contracts and withdraws into its burrow to avoid being eaten.

Anatomical adaptaions are any structure that enhances the survial of the organism. Bacteria that have flagella to help them move independently.

Physiological/biochemical adaptations are adaptaions that ensure correct functioninf of cell processes. Producing the correct enzymes to respire.

A well adapted organism will be able to: find enough food or photosynthesise well, find enough water, gather enough nutrients, defend itself from predators and diseases, survive the physical conditions of its enviroment, respond to changes in its enviroment and still have enough energy to reproduce successfully.

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Xerophytic plant 1

  • xerophyte is a plant that is adapted to living in very dry conditions.

Behavioural adaptations

  • Some plants close their stomata when little water is avalible. This conserves water so they don't wilt.
  • Some plants only open their stomata at night. This conserves water because less water is lost from the leaves at night when it's cooler and more humid.
  • Some plants fold or roll their leaves when water is in short supply. Reduces water loss by trapping moist air in the folded leaf, reducing water vapour potential gradient for diffusion out of the leaf.
  • Some plants open there stomata when they are short of water. This causes leaves to wilt so less surface area is exposed to the sun.

Anatomical adaptations

  • Shallow roots that spread out over a wide area. Allows a plant to absorb a large amout of water when avalible.
  • Long roots. Enables plant to reach water that is deep underground.
  • Fleashy stem or leaves. Water storage.
  • Reduced size of leaves. Reduces the surface area for evapouration.
  • Waxy leaves. So water can only leave through stomata.
  • Leaves that are curled, folded, hairy or have stomata sunk in pitsTrap a layer of moist air nect to stomata, reducing water loss by transpiration.
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Natural selection

  • In natural selection the best-adapted organisms in a population can outcompete thoses that are less well-adapted. They are selected by the enviroment to  survive a reproduce and pass on their variations to the next generation.

Natural selection leads to evolution as over time changes in the proportion of alleles in the gene pool occur.


  • Avalibilty of suitable food.If an individual is adapted to eat the avalible food it has a selective advantage.
  • Predator. An individual that is adapted to aviod being seen and eaten, or to escape has a selective advantage.
  • Dieseases. If an organism can survive a disease it has a selective advantage.
  • Physical and chemical factors. 
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  • Speciation is the formation of a new species.

Speciation is a long , slow accumulation of changes that result in individuals no longer being able to interbreed freely to produce viable offspring. It takes many generations, although bacteria and single-celled organisms can do this a couple of hours.

Speciation occurs because of a reproductive barrier, organisms are unable to breed with others in the group. Variation may occur in part of the group and spread through generations in a populations in a group via reproduction, but if it can't spread to the whole group only part of the group will benefit. Some members will become different to the others and will no longer be able to interbreed.

reproductive barrier is any factor that prevents effective interbreeding between members of the species

  • Allopatric speciation occurs when organisms of the same species become seperated by geographical barriers. Over time members of the two populations become so different they can't inerbreed and are considered to be two different species. E.g. Different islands.
  • Sympatric speciation occurs within one area - a factor other than geographical seperation had prevented free interbreeding between members of the species. E.g. Unrecognised courtship dance, sexual organs are no longer compatible, biochemical change prevents fertilisation.
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A group of individuals may evolve into a new species if:

  • a population of the species migrated to a new enviroment.
  • an enviromental change affects only some populations of the species.
  • A reproductive barrier occurs.

If part of a species evolves into a new species this increases diversity.

  • selection pressure is an external pressure that drives evolution in a particular direction.
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Conservation of species

  • Extinction is when a species ceases to exsist.

Extinction reduces biodiversity.

Human activities that reduce biodiversity and cause extinction include:

  • Over-harvesting.
  • Killing for protection.
  • Killing to remove competition for food.
  • Pollution.
  • Habitat destruction.
  • Introduction of new predators and competitors to natural flora and fauna.
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Conservation in situ 1

  • Conservation in situ is the conservation of a species with its natural enviroment.

Legislations can be passed to stop activities such as hunting, logging and clearing land for development and agriculture.

Conservation parks

Principles for choosing a reserve park must include:

  • Comprehensiveness. How many species are represented in the area and what are the enviromental conditions.
  • Adequacy. Is the area large enough.
  • Representativeness Is there a full range of diversity.


  • Conservation occurs in natural enviroment.
  • Permanently protects biodiversity and represents examples of ecosystems.
  • Facilitates scientific research.
  • Permanently protects significant elements of natural and cultural heritage.
  • May be possible to restore the ecological integrity of the area.
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Conservation in situ 2

Conservation reserves in the UK

  • National parks
  • National Nauture Reserves (NNR)
  • Sites of Special Scientific Interest (SSSIs)
  • Local nature reserves

Where biodiversity has been loss it's posible to rebuild it

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Conservation ex situ 1

  • Conservation ex situ is conservation that occurs outside a species natural habitat.

Breeding programmes may occur within wildlife parks they concentrate on breeding endangered species. Breeding programmes can help increase the number of individuals of an endangered species and enable repopulation by introducing captive-bred animals to the wild.


  • Failure to breed successfully.
  • Space is limited, limiting the number of individuals, restricting the genetic diversity.
  • Lack of variation.
  • Have to survive reintroduction to the wild, find food and survive preditation.
  • Difficulty with acceptance from wild members of the species.

Modern techniques:

  • Sperm freezing, artificial insemination, in vitro fetilisation and embryo-transfer.
  • Reproductive physiology is unique to the species and further research is required to ensure that techniques as uses effectively. Can be carried out on domestic species.
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Conservation ex situ 2



  • Have a dormant stage. Seed.
  • Seeds are produced in large numbers and can be collected without disturbing the ecosystem.
  • Seeds can stored and germinated in protected surroundings.
  • Seeds can be stored in large numbers without occupying too much space.
  • Plants can oftern be bred asexually.
  • Ample supply of individuals for research as botanical gardens can increase the number of individuals very quickly.
  • Captive-bred individuals can be replanted in the wild.


  • Collection of wild seeds will cause a disturbance.
  • Collected samples may not hold a representative selection of genetic diversity.
  • Seeds stored for any length of time may not be viable.
  • Plants bred asexually with be genetically identical reducing genetic diversity.
  • Conclusion from research on small sample may not be valid for the whole species.
  • Seeds from the same species may not succeed in another area as they're genetically different.
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Conservation ex situ 3

Seed banks

A collection of seed samples that can remain viable for decades.


  • Seeds are stored in very dry or freezing conditions to prolong their viability.
  • Seeds must be tested periodically to check their viability.
  • Seeds will be planted in petri dishes of nutrient agar and kept in  controlled conditions.
  • The germination rate is measured along with the success of germination.
  • This enable scientist to monitor the condition of the stored seeds.
  • Research continues into the physiology of seed dormancy and germination.
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The Convention on International Trade in Endangered Species of Wild Fauna and Flora is an international agreement. The overall aim is to ensure that international trade in specimens of wildlife doesn't threaten their survival.


  • Regulate and monitor international trade in selected species of plants and animals.
  • Ensure that international trade doesn't endanger the survival of populations in the wild.
  • Ensure that trade of wild plants is prohibited for commercial purposes.
  • Ensure that trade in artificially propagated plants is allowed subject to permit.
  • Ensure that some slightly less endangered wild species may be traded subject to a permit, as agreed between the exporting and importing countries.
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Convention on Biological Diversity

The Convention is dedicated to promoting sustainable development.


  • Conservation of biological diversity.
  • Sustainable use of its components.
  • Appropriate shared access to genetic resources.
  • Appropriate sharing and transfer of scientific knowledge and technologies.
  • Fair and equitable sharing of the benefits arising out of the use of genetic resources.

The convention encourages cooperation between coutnries and states. It states that partner states must adopt ex situ consevation facilities, mainly to complement in situ measures.E.g. Zoos, botanical gardens and seed banks.

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Environmental impact assessment

  • Enviromental impact assessment (EIA) is a procedure to assess the likely significant effects that a proposed development may have on the enviroment.

An EIA takes into account:

  • Size of the development.
  • Enviromental sensitivity of the location.
  • Types of impact expected.

If an EIA is required there are 3 stages to the procedure:

  • The developer complies an environmental statment, which includes and assessment of local biodiversity and the effect development is likely to have on biodiversity.
  • The environmental statement is published.
  • The authority take it into account when making a planning decision.
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