Transcript B3 Life on Earth - Trinity School Nottingham

Life on Earth Revision
Variation of Life on Earth
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All living things, both those alive and
those that are now extinct all originate
from the simple living things that first
appeared 3500 million years ago.
Evidence for evolution comes from:
– Fossils
– DNA testing
Natural Selection
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Natural selection involves:
Variation
Competition
Increased chance of survival
Reproduction
Increases numbers in population
Selective Breeding
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Selective Breeding involves:
Selecting individuals with desired features
Breeding them
Selecting offspring with desired features
Breeding them
Increasing numbers with desired features
Multi-cellular Organsism
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Evolution of multi-cellular organisms
has lead to;
– The development of receptor and effector
cells.
– These are linked by neurones.
– The neurones link via the CNS
(See Brain and Mind)
Theories of Evolution
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Lamark – suggested organisms developed
through an inner urge to improve.
Cuvier – suggested the fossils in layers of
rock were due to God wiping old species out
with catastrophes , e.g. Noah’s Ark.
Darwin – suggested evolution occurred by a
process of natural selection or survival of
the fittest.
Darwin’s Theory
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Was rejected at first for religious
reasons as the Bible was taken literally
at the time.
Was eventually accepted because it
explained how evolution occurred.
Data and Theories
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Understand the difference between
data and theories.
Appreciate that data could be
explained by a number of theories.
Appreciate that theories require
original thought.
Understand why theories are accepted
or rejected.
Key Terms with Theories
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Understand the terms
– Corroborate; make more certain
– Confirm; strengthen, verify.
– Falsify; forge, misrepresent.
– Prove; to establish as truth
Causes of Variation
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Random changes in the DNA called
mutations occur.
If in sex cells these are passed on to the
offspring.
Sometimes these changes gives increased
chances of survival.
The frequency of the mutation then starts to
increase.
This can eventually lead to new species.
Evolution
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Random Mutation.
Random Breeding.
Natural Selection.
Human Evolution
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Humans species have evolved from a
common ancestor.
All other hominids have become extinct.
The evolution of intelligence is very
important to the evolution of humans.
The ability to learn from experience has
given humans a selection advantage.
Under Pressure
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Organisms are dependent on the
environment and other species.
Organisms compete.
Large changes in the environment can
result in extinction of a species.
Extinction of one species can then
affect other species in the food web.
Under Pressure (cont.)
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Changes that can affect an organism
include;
Major change in conditions
A new species that is a competitor, predator
or disease.
Another organism in the food web becomes
extinct.
Many species have become extinct,
sometimes mass extinctions occur e.g.
dinosaurs.
Biodiversity
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There is evidence of an increasing rate of
extinctions.
Retaining biodiversity may be important for
food and medicines.
A species has less chance of becoming
extinct in an ecosystem that is diverse.
Maintaining diversity is an important part of
using the environment in a sustainable way.
Origins of Life
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The first living things developed from molecules
that could copy themselves (DNA).
These molecules were produced by the unique
conditions at the time.
If conditions had been different, natural selection
could have produced different results.
Although there is no proof of life elsewhere, there
are so many galaxies, stars and planets that some
scientists think life elsewhere in the Universe is
likely.