Summary
Summary Evolution part 1
- Course
- Biology
- Institution
- Kloof High School
Grade 12 / matric biology - evolution part 1
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Evolution:A hypothesis is an educated guess, based on observation. Usually, a hypothesis can be supported or refuted
through experimentation or more observation. A hypothesis can be disproven, but not proven to be true.
A scientific theory is an accepted hypothesis. A theory summarizes a hypothesis or group of hypotheses that
have been supported with repeated testing. A theory is valid as long as there is no evidence to dispute it.
Therefore, theories can be disproven. If evidence accumulates to support a hypothesis, the hypothesis can
become accepted as a good explanation of a phenomenon.
A law generalizes a body of observations.
The theory of evolution – is it a theory?
It is time for students of the evolutionary process, especially those who have been misquoted and used by the
creationists, to state clearly that evolution is fact, not a theory, and that what is at issue within biology are
questions of details of the process and the relative importance of different mechanisms of evolution.
It is a fact that the earth with liquid water is more than 3.6 billion years old.
It is a fact that cellular life has been around for at least half of that organized multicellular life is at least
800 million years old.
It is a fact that major life forms now on earth were not all represented in the past. There were no birds
or mammals 250 million years go.
It is a fact that major life forms of the past are no longer living. There used to be dinosaurs and
Pithecanthropus, and there are none now.
It is a fact that all living forms come from previous living forms. Therefore, all present forms of life arose
from ancestral forms that were different.
“No person who pretend to any understanding of the natural world can deny these facts anymore than
they can deny that the earth is round, rotates on its axis, and revolves around the sun.” - Lawrence
A population is a group of organism of the same species inhabiting a more or less defined area such that
random interbreeding can occur.
Biodiversity is the variety of plants and animals in a habitat.
Extinction is when there are no living examples yet. Background extinction is the normal occurring loss of
organism. Doesn’t involve mass destruction.
A species is a group of organism, which share common characteristic and can produce fertile young.
Variation within the species:
Meiosis: Crossing over at prophase and the random arrangement of genes at metaphase 1 and 2.
Mutations: The proteins in the amino acids are in a different sequence and the nitrogen bases in the
DNA are in a different sequence.
Reproduction: Selection of a mate and the fusion of egg and sperm is entirely random.
Jeane Baptiste de Lamarck’s theory of evolution:
Jean Baptiste de Lamarck published theory of evolution in 1809.
The law of use and disuse – Parts of an organisms body, which were useful to an organisms in dealing with the
environment, became bigger and stronger, while those useless parts became reduced or faded away.
The law of inheritance and acquired characteristics – If an animal acquired a characteristic during its life
they would it onto their children.
He believed that giraffes got long necks after a lifetime of stretching up for leaves on high trees and then passing
this on to their offspring who continued to stretch and so on, generation after generation until we got the really
long-necked giraffes of today (the law of use and disuse)(the law of inheritance and acquired traits).
He also believed that snakes used to have legs but because they didn’t use their legs they eventually
disappeared (the law of use and disuse).
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