Transcript Evolution - Noadswood Science

Theories of Evolution
L.O: To understand the theory of
natural selection and why it was only
gradually accepted over other theories
How has the theory of evolution
changed over time?
• Up to the 18th Century people believed
god created the world.
• At the beginning of the 19th century
scientists came up with new ideas.
- e.g. Lamarck and the inheritance of
acquired characteristics, all animals
evolved from worms.
- Darwin and Natural Selection.
Evolution
Evolution is the slow, continual change of
organisms over a very long time. All living
things on the Earth have developed from
the first simple life forms that arrived
3,000,000,000 years ago.
One of the effects of evolution is that species will become
better adapted to their environment. If these species
don’t adapt they may become extinct due to being unable to
deal with any of these factors…
1) Increased competition
2) Changes in the environment
3) New diseases
4) New predators
Explain why organisms
adapt (evolve) and what
may happen if they don’t.
Darwin vs Lamarck
09/04/2016
Darwin wasn’t the first to come up with evolution – he was
simply the one credited with explaining how it worked (i.e.
Natural Selection). An earlier scientist called Lamarck
explained evolution by different means:
The giraffe has a long neck
because it “stretches” its neck to
reach the food, and these long
necks are passed on to their
offspring. Organs which aren’t
used will eventually disappear.
Jean Baptiste
Lamarck
(1744 - 1829
Darwin’s Theory
1) Each species shows variation:
Get off
my land
2) There is competition within each
species for food, living space,
water, mates etc
3) The “better adapted” members of
these species are more likely to
survive – “Survival of the Fittest”
Gutted!
Yum
4) These survivors will pass on their
better genes to their offspring who
will also show this beneficial variation.
Evolution
My key observations:
1) All living things produce more
offspring than survive to adulthood
2) In spite of this, population sizes
remain roughly constant
3) Variation exists among species
4) Characteristics can be passed on
from one generation to the next.
These observations led me to the
conclusion that species evolve over a
along period of time by a mechanism
called “Natural Selection”. The main
evidence for this is from fossil
records.
The theory of evolution by natural selection was only gradually
accepted because:
■ the theory challenged the idea that God made all the animals and
plants that live on Earth
■ there was insufficient evidence at the time the theory was
published to convince many scientists
■ the mechanism of inheritance and variation (Mendel) was not
known until 50 years after the theory was published.
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KEY IDEA:
The stages of natural selection; variation, competition, survival, reproduction can always be applied to
explain evolution. Mutation is a form of variation.
1. (i) Lamarck stated that as a giraffe stretches up to eat leaves from a high tree, its neck gets longer. This
characteristic would be passed on to the next generation. Use ideas about how you know characteristics
are inherited to explain why we know that Lamarck’s statement was wrong. (3 marks)
(ii) ‘Evolution means that eventually organisms will become more complex.’
Discuss evidence for and against this statement.
(4 marks)
(iii) Warfarin can be used as a rat poison. The number of rats that are resistant
to warfarin is increasing. Some people, wrongly, think this is because rats
that come into contact with warfarin are developing a way of becoming
resistant to the poison. Use ideas about mutation to explain what really
happens.
(3 marks)
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KEY IDEA:
The stages of natural selection; variation, competition, survival, reproduction can always be applied to explain
evolution. Mutation is a form of variation.
1. (i) Lamarck stated that as a giraffe stretches up to eat leaves from a high tree, its neck gets longer. This
characteristic would be passed on to the next generation. Use ideas about how you know characteristics are inherited
to explain why we know that Lamarck’s statement was wrong.
(3 marks)
Giraffes have genes for neck length (1) giraffes with a long neck gene pass it on to their offspring (1) this makes long
neck giraffes more able to reach leaves higher on a tree (1) reaching up or stretching cannot change this gene.
(ii) ‘Evolution means that eventually organisms will become more complex.’
Discuss evidence for and against this statement.
(4 marks)
There is evidence that life on Earth evolved from single celled organisms that have become more and more complex.
(1) Each new variation has enabled the organism to become more successfully adapted to the environment it lives in
(1)
However, there are millions of species of different bacteria on Earth (1) that have adapted to their environment over
time and have not changed for millions of years (1) so will not evolve more.
(iii) Warfarin can be used as a rat poison. The number of rats that are resistant
to warfarin is increasing. Some people, wrongly, think this is because rats
that come into contact with warfarin are developing a way of becoming
resistant to the poison. Use ideas about mutation to explain what really
happens.
(3 marks)
The resistance to warfarin is a chance occurrence (1) caused by a genetic mutation (1). A rat that has developed a
mutated gene resistance passes it on to its offspring (1) who will also be resistant to the poison.
Daffodils
• Follow this hyper-link to a question
about Daffodils
• R:\Science\Year9\PMi\9A1\BIOLOGY
1\Biology new\lesson 36 darwin and
lamarck\Daffodils..doc