Download Selection - Science in Progress

EVOLUTION
Look at this picture which shows the process of evolution
CHANGE
Using only one word explain the meaning of evolution
Let's work out a more specific definition …..........
Selection
Offspring
Best
Heritable
Competition
Struggle
Population
Evolution: process of change in the
inherited traits of a population of organisms
from one generation to the next
(processed at the level of the genes)
How does evolution occurr ?
Promotes diversity of characters in the offsprings
by providing genetic variation
SEXUAL
REPRODUCTION
Offers the opportunity to produce recombinant types
that can make the population better able to keep up
with changes in the environment.
OFFSPRING ARE GENETICALLY UNIQUE FROM:
Indipendent assortment (2 n possibilities)
Crossing over
Random fusion of gametes
They provide the genetic diversity
that makes natural selection possible.
MUTATIONS
the row material of
evolution
Phenotyipic change in the
offspring
Somatic cell
Germ line
cell
NATURAL
SELECTION
Organism with favorable traits are more likely to survive
and
to leave more offspring better suited for their enviroment
In this image appears Alfred Wallace and Charles Darwin,
both came up with the theory of evolution.
Look trough these web sides, work in pairs and make an
interview each other with questions like these:
•Where and when they were born;
•Where and when they died;
•What they did;
•Their nationality;
•They were known because.…;
•The problems associated with their theory….
•http://en.wikipedia.org/wiki/Alfred_Russel_Wallace
•
Charles Darwin – the boy
Charles Darwin was born on 12th February 1809
in Shrewsbury, England.
He went to boarding school in Shrewsbury and
in 1825 went to Edinburgh University to study
medicine.
Whilst in Edinburgh Darwin investigated marine
invertebrates and started to develop a growing
interest in natural history.
In 1827, at the age of 18, Darwin realised he did
not like the study of medicine and could not bear
the sight of blood or suffering. He left Edinburgh
for Cambridge University with the idea of becoming
a clergyman.
Charles Darwin – the young man
Whilst at Cambridge Darwin met a number
of people who were influential in shaping
his career.
His cousin William Darwin Fox, who was a
keen collector of beetles.
John Henslow, who studied and lectured
on plants.
Professor Adam Sedgewick, who taught
him about geology during an expedition to
Wales in 1831.
In August 1831, Henslow wrote to Darwin
inviting him to become a naturalist for
Captain Fitzroy on the survey ship the
Beagle.
Darwin and the Voyage of the Beagle
1831 - 1836
The mission of H.M.S. Beagle
was to map the oceans and
collect oceanographic and
biological information around
the world. The map indicates
the ship's path, and the inset
shows the Galapagos Islands,
whose organisms were an
important source for Darwin's
ideas on natural selection.
Charles Darwin and Natural Selection
An idea that would change the world
Charles Darwin developed his
theory of evolution by natural selection
using FOUR important OBSERVATIONS
which led him
to TWO DEDUCTIONS.
Up to 7 kittens
Female pig (Meishan)
Female rabbit
Up to 60 kitten
One of Darwin’s first observations was that
Chick
all living things are capable of producing
more offspring than are needed to replace
their parents.
Do they all survive to become adults?
1. All organisms produce more offspring than survive to adulthood
English economist Thomas Robert Malthus (1766 - 1834)
Both Darwin and Wallace were influenced by the ideas of
the economist Thomas Malthus, who in 1798
published An Essay on the Principle of Population.
Malthus argued that because the rate of human
population growth is greater than the rate of increase in
food production, unchecked growth inevitably leads to
famine
Darwin saw parallels throughout nature.
Herds of many animals live on
the plains of Africa:
wildebeest, zebra, gazelles
etc.
Each year many of the females give
birth to young, but the overall
population sizes..............
Darwin’s second observation was that the numbers of many
different species of animals and plants tend to stay fairly constant
over long periods of time.
There are a number of factors
which keep the population
numbers stable, including
competition
for
food,
predation and disease
2. Populations remain more or less constant in numbers
Look at these giraffes.............
Do they belong to the same specie?
Are they identical?
Darwin’s third observation was
that all living things vary slightly
in colour, shape, size or
behaviour.
Different colourings and skin patterns found in the giraffe.
3. Members of the same species show
variation in characteristics
Which is the differerence between these characteristics?
Darwin’s fourth observation was that many features are
passed on from parent to offspring.
Some inherited characteristics
are quite easy to see in humans:
Eye colour
Hair colour
Some are not so easy to see:
Blood group
Mendel 1822-1884
4. Some characteristics are inherited and so
passed on to the next generation
French biologist Jean Baptiste
Lamarck (1744–1829)
“The inheritance of acquired characteristics”
“Change through use and disuse”:
When environments changed, organisms had to change
their behavior to survive.
If a giraffe stretched its neck for leaves, for example, a
"nervous fluid" would flow into its neck and make it
longer.
Its offspring would inherit the longer neck, and continued
stretching would make it longer still over several
generations.
Meanwhile organs that organisms stopped using would
shrink.
Observations
Observations:
4. Some characteristics are inherited and so passed
on to the next generation
1. All organisms produce more offspring than survive to adulthood
2. Populations remain more or less constant in numbers
3. Members of the same species show variation in characteristics
4. Some characteristics are inherited and so are passed on to the
next generation
DEDUCTIONS?
CONCLUSIONS?
Pigeon and
sparrow
Describe what's happening in
these pictures..............
Spider and fly
Polar bears
A. All organisms are involved in a struggle for survival.
Striped tigers and leopards spots: WHY?
It is an adaptation to the enviroment in which they live.
Camouflage themselves to ambush their prey too
Pygmy seahorse camouflaged against fan coral
B. Some individuals are better adapted
to their environment than others.
Survival of the fittest
The individuals that are best adapted to their environment are most
likely to survive and have the chance to reproduce, therefore
passing on their useful adaptations to the next generation.
Those individuals that are the least well adapted do not survive long
enough to breed.
Silverback mountain gorilla
Male African lion
These ideas formed the basis of Darwin’s theory of evolution by natural selection.
English naturalist, explorer, geographer, anthropologist, and biologist
Alfred Russel Wallace (1823 –1913)
Alfred Russel Wallace,
was studying the biota of the Malay
Archipelago.
Wallace asked Darwin to evaluate the
manuscript, in which Wallace proposed a
theory of natural selection almost
identical to Darwin's.
At first Darwin was dismayed, believing
that Wallace had preempted his idea.
24 Novembre 1859
The origin of species
A population showing
variation in colour.
Continuous or
discontinuous?
There is lots of food so your population survives and
reproduces. Add 5.
The bright yellow of some of your offspring attracts predators.
All but two of them get eaten.
There’s lots of food and hiding places for the green and
blue, but the red ones can’t hide and get eaten.
Plenty of food and its spring so another 10 offspring are
born, they are a variety of colours.
Plenty of food and its spring so another 10 offspring are
born, they are a variety of colours.
It’s winter and 5 of your population die
Its mating time again, blue and green mate and produce
5 green and 2 blue offspring. A mutation also produces
2 red offspring
Its mating time again, blue and green mate and produce
5 green and 2 blue offspring. A mutation also produces
2 red offspring
There is lots of food, and all reproduce 2 offspring, but
the white are better at finding water and hiding from
predators so they produce 5 offspring
There is lots of food, and all reproduce 2 offspring, but
the white are better at finding water and hiding from
predators so they produce 5 offspring
The bright red colour attracts mosquitoes carrying a
deadly disease. They all die.
The bright red colour attracts mosquitoes carrying a
deadly disease. They all die.
It is a particularly hot summer, blue and green are poor
temperature regulators; white and yellow, which reflect
heat, are more likely to survive.
It is a particularly hot summer, blue and
green are poor temperature regulators;
white and yellow, which reflect heat, are
more likely to survive.
When food is plentiful again the remainder mate and
produce 5 offspring some white and some yellow.
When food is plentiful again the remainder mate and
produce 5 offspring some white and some yellow.
A scientist finds this population and reports that this
species occurs in two colours. He says they have
adapted to their habitat. What does he mean?
What is the population?
Has it changed?