Unit 2 - Speciation
Fossils from soft bodied animals, such as jellyfish, are rare.

Unit 2 - Speciation

Speciation is the formation of a new species from an original species. The original species are sometimes called the founder species. This GCSE Biology quiz looks at the causes of and the evidence for speciation.

A species is generally defined as a population of living organisms that are able to breed naturally and produce fertile offspring (although it cannot apply to organisms that reproduce asexually such as bacteria). Members of a species breed at a rate that produces more offspring than can be supported by a habitat. Some of the offspring do not reach maturity because of starvation, predation or disease. Those who inherit features that enable them to survive to breeding age are said to be better adapted and they are more likely to pass on the genes that have made them successful. This is the basis of natural selection and evolution.

The formation of a new species occurs very slowly through natural selection, where the best adapted individuals survive and the least well adapted ones die off. Over a very long time the founder species becomes extinct and a new one has evolved. The usual cause of speciation is geographic isolation but anything that can cause reproductive isolation would have the same effect.

Plate tectonics can create geographical barriers as a result of Earth movements such as an earthquake changing the course of a river. If this crosses the habitat of a species, the population can be split into two sub-groups, reproductively isolating them. Random mutations in the genes and slightly different environmental conditions cause each sub-group to evolve differently. Eventually, natural selection in the two groups can produce new genotypes and phenotypes. They eventually reach the point where it would be impossible for them to interbreed successfully, should the isolating feature ever disappear. Perhaps the ultimate isolation is continental drift which splits whole continents apart. There is plenty of evidence in the fossil record of speciation, including human evolution.

Take this quiz and test yourself on speciation - the formation of a new species from a founder species.

A species is an interbreeding population capable of producing what?
Infertile offspring
Fertile offspring
No offspring
Donkeys and horses are different species but can interbreed to produce a mule, but very few mules are fertile
Speciation is the formation of new...
This happens through reproductive isolation and natural selection
Speciation can be studied using which of the following?
Recording data
The fossil record shows the adaptations over time which can lead to new species
What are fossils?
The remains of dead organisms from many years ago that are preserved in rocks
Plants found in coal and oil
Rocks and stones
Little creatures
DNA studies from human fossils have helped us to understand the relationships between the different anscestral species of modern humans
Species survive if they are...
well adapted
poorly adapted
not extinct
Well adapted means that they are suited to life in their environment
Which word describes species which have died off?
Badly adapted species will not breed successfully and so their genes will be removed from the gene pool by natural selection
Which of the following is not a cause of extinction?
Changes in the environment over geological time
New predators
Short term environmental changes
The environmental changes needed for extinction take place over many years
Fossils from soft bodied animals are...
found everywhere
found in the sea
Soft bodied animals rarely leave a fossil behind as the body just decays. Bones, shells and plant parts are more easily preserved in rock and are more common
Which of the following is an example of geographical isolation?
A mountain separating two populations
The Sun
An isolation mechanism is needed to separate the two populations so that they can evolve into two different species
Genetic variation provides the basis for new species. Variation means that individuals are...
the same
Genetic variation is a random process. Changes that make an organism better adapted are more likely to be passed on to future generations by natural selection
You can find more about this topic by visiting BBC Bitesize - Evolution

Author:  Donna Maria Davidson

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