Upload
sureshthevan
View
219
Download
0
Embed Size (px)
Citation preview
7/27/2019 03 Evolution
1/3
- GCSE Bitesize - Evolution
//www.bbc.co.uk/schools/gcsebitesize/science/edexcel/classification_inheritance/evolutionrev_print.shtml[10/21/2013 8:12:01 PM]
Science
Evolution
Evolution has taken place over millions of years and
scientists believe this is the reason why all living things on
Earth exist today. There are different views and theoriesabout the origin of life and the evolutionary process.
English naturalist Charles Darwin wrote one of the f irst
major scientific books on this subject.
Charles Darwin
Charles Darwin was an English naturalist who
studied variation in plants and animals during a
five-year voyage around the world in the 19th
century. He explained his ideas on evolution in
a book called, 'On the Origin of Species',
published in 1859. This shows how species
adapt and change by:
variation in any population of
organisms there will be some differences
over-production many organisms produce more
offspring than necessary
struggle for existence there is competition for survival
and resources between the organisms
survival - those with helpful characteristics are more
likely to survive to breed
useful characteristics inherited by the offspring
gradual change of the species over a period of time asuseful characteristics are passed to offspring.
Darwin's ideas caused a lot of controversy, and this continues
today, because they can be seen as conflicting with religious
views about the creation of the world and the creatures living in
t.
Charles Darwin
(1809 - 1882)
7/27/2019 03 Evolution
2/3
- GCSE Bitesize - Evolution
//www.bbc.co.uk/schools/gcsebitesize/science/edexcel/classification_inheritance/evolutionrev_print.shtml[10/21/2013 8:12:01 PM]
The basic idea behind the theory of evolution is that all the
different species have evolved from simple life forms. These
simple life forms first developed more than 3 billion years ago
(the Earth is about 4.5 billion years old). The timeline below
shows some of the key events in the evolution of life on Earth,
from the first bacteria [bacteria: Single-celled microorganisms,
some of which are pathogenic in humans, animals and plants.
Singular is bacterium. ] to the first modern humans.
You can see a more detailed history of life timeline on BBC
Nature.
Support for Darwins theory
Antib iot ic-resistant bacteria
Microorganisms such as bacteria
[bacteria: Single-celled
microorganisms, some of which are
pathogenic in humans, animals and
plants. Singular is bacterium. ] and
viruses [viruses: ultramicroscopic
non-cellular organisms that replicate
themselves inside the cells of living
hosts ] reproduce rapidly and can
evolve in a relatively short time. One
example is the bacterium E. coli. Its DNA [DNA : The material
nside the nucleus of cells, carrying genetic information. DNA
stands for Deoxyribonucleic Acid. ] can be damaged or changed
during replication, and most of the time this causes the death of
the cell. But occasionally the mutation is beneficial (to thebacteria). For example, it may allow resistance to certain
antibiotics [antibiotics : Substances that kill bacteria. ]. When
those antibiotics are present, the resistant bacteria have an
advantage over the bacteria that are not resistant. Antibiotic-
resistant strains of bacteria are an increasing problem in
hospitals.
E. coli bacteria (Photo from
Rocky Mountain
Laboratories, NIAID, NIH)
http://www.bbc.co.uk/nature/history_of_the_earth#timelinehttp://www.bbc.co.uk/nature/history_of_the_earth#timelinehttp://www.bbc.co.uk/nature/history_of_the_earth#timelinehttp://www.bbc.co.uk/nature/history_of_the_earth#timeline7/27/2019 03 Evolution
3/3
- GCSE Bitesize - Evolution
//www.bbc.co.uk/schools/gcsebitesize/science/edexcel/classification inheritance/evolutionrev print.shtml[10/21/2013 8:12:01 PM]
DNA
Scientists can now examine the DNA from different species of
organism and use the data produced to see how closely related
the two species are to each other. By collecting a lot of this data,
scientists can compare the results with conventional ideas about
how organisms have evolved. What they found was that DNA
data supported the conventional theory of evolution.
Validating evidence
Darwins theory of evolution is still known as a theory but it is
widely accepted within the scientific community. This wasnt the
case when it was first published as there was very little scientific
evidence to back up his ideas. Now we have evidence from
DNA and studies on resistant bacteria to help validate (confirm)the theory. All new scientific evidence is assessed by the
scientific community through:
scientific journals
the peer review process
scientific conferences.
Now try a Test Bite.
Back to Revision Bite
http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/classification_inheritance/evolution/quiz/q66565819/http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/classification_inheritance/evolutionrev1.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/classification_inheritance/evolutionrev1.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/classification_inheritance/evolution/quiz/q66565819/