Reproductive Strategies

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Evolution He was particularly interested in the size and They believe that they are special creations by
The process of evolution has enriched our world shape of their beaks and the foods they ate. God.
by increasing the number of species present on It became clear to Darwin that each species of
the earth today. finch had developed from a common Eldridge and Gould:
ancestor. These American scientists suggested that new
Theory of Evolution: However, the different food types of each island species arise very quickly and then change over
The theory of evolution was introduced by Darwin had required the birds to adapt a different shaped millions of years.
during a visit to the Galapagos Islands. beak in order to access the food available. They suggested that only a few individuals are
He collected information there and using This is called ADAPTATIVE RADIATION. involved.
geological and fossil evidence to support the As a result of this it would be rare to find an
theory that many changes can be seen in a Adaptive Radiation: intermediate species as a fossil record.
species over a period of time called the natural This is also called Divergent Evolution. When the environment changes for the worse, it
selection. When a group of organisms all possess a causes migration as well as evolution of different
structure that appears to have come from a species.
Natural Selection: common ancestor and which has the same Those unable to migrate or evolve die out.
For a species to survive it must reproduce. microscopic structure and body position, as When these changes in the environment are very
However, the population is limited by well as other features, they are said to have extreme, MASS EXTINCTIONS can occur.
environmental factors and so remains more or homologous structures.
less constant over time. These may have become specialised in each Mass Extinctions:
group for a particular function. An example of Natural selection leads us to believe that
There is competition between the individuals of this would be the pentadactyl wing which is evolution is a slow gradual change in a species
the same species (intraspecific) or between shared by all mammals but may be used as a over time.
members of different species (interspecific) for hand, a flipper and a wing. However, evidence from other scientists show
the resources available. They look different in different species and are that mass extinctions can take place.
used for different things because of the These are where large numbers of species can
Since there is variation within a population, some particular selection pressures on the species. be wiped out for failing to adapt to the new
individuals will be less well adapted to a particular surroundings or changes in the environment.
environment. These less well adapted individuals The Opposite of Adaptive Radiation: Mass extinctions are events resulting in the
are forced to compete for survival as the selection This is called Convergent Evolution and these elimination of huge numbers of a species.
acts on the phenotype of the individual. are where whole structures that on first To date, there has been FIVE MASS
appearance seems to be similar but are actually EXTINCTIONS and another one is due very very
The individuals which fail to reproduce, and die. unrelated. soon...
The more successful members survive and Examples include insect and bird wings, the eye
reproduce to pass on their genes to the next of a mollusc and of a vertebrate. Why Did the Dinosaurs Die Out:
generation. These structures are said to be analogous. In 65 million years ago the dinosaurs became
However, adaptions are environment specific. these cases, selection pressures from the extinct after becoming the most dominant
An advantageous characteristic can become environment in which they live have used species on Earth through adaptive radiation.
disadvantageous if the environment changes in a particular structures to be advantageous. This period of adaptive radiation made the
particular way. dinosaurs to branch out into many different
Palaeontology: species of dinosaur and allowed them to be the
Galapagos Island Finches: This is the study of fossil remains. stronger competitor compared to any other
Darwin studies 14 different types of finch, and he Ordering the fossils into geological sequence species at the time.
quickly realised that the birds had come from the can form a picture of how groups of organisms
mainland and that the winds must have helped lived.
them since they couldn't fly very far.
On each island, the bird's shows slightly different Creationist Beliefs:
adaptations compared to those on other islands. Creationists believe that the intermediate forms
are not evidence of evolution.

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