EVOLUTION
Dec 28, 2015
EVOLUTION
Look at this picture which shows the process of evolution
Using only one word explain the meaning of evolution
CHANGE
And from a biological
point of view?
Let's work out a more specific definition …..........
Struggle
Adaptation
Enviroment
Selection
Competition
Heritable
Population
Offspring
Species
BestBest
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:
Crossing over
Indipendent assortment (2 n possibilities)
Random fusion of gametes
MUTATIONS
the row material ofevolution
They provide the genetic diversity
that makes natural selection possible.
Somatic cellGerm line
cell
Phenotyipic change in the offspring
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.
The mission of H.M.S. Beagle The mission of H.M.S. Beagle was to map the oceans and was to map the oceans and collect oceanographic and collect oceanographic and biological information around biological information around the world. The map indicates the world. The map indicates the ship's path, and the inset the ship's path, and the inset shows the Galapagos Islands, shows the Galapagos Islands, whose organisms were an whose organisms were an important source for Darwin's important source for Darwin's ideas on natural selection.ideas on natural selection.
Darwin and the Voyage of the BeagleDarwin and the Voyage of the Beagle
1831 - 18361831 - 1836
Charles Darwin and Natural SelectionCharles 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.
Female rabbit
Female pig (Meishan)
Up to 60 kitten
Up to 7 kittens
One of Darwin’s first observations was that
all living things are capable of producing
more offspring than are needed to replace
their parents.
Chick
Do they all survive to become adults?
1. All organisms produce more offspring than survive to adulthood
Both Darwin and Wallace were influenced by the ideas of the economist Thomas Malthus, who in 1798published 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.
English economist Thomas Robert Malthus (1766 - 1834)
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.
2. Populations remain more or less constant in numbers
There are a number of factors which keep the population numbers stable, including competition for food, predation and disease
Darwin’s third observation was that all living things vary slightly in colour, shape, size or behaviour.
Look at these giraffes.............
Do they belong to the same specie?
Are they identical?
3. Members of the same species show
variation in characteristics
Different colourings and skin patterns found in the giraffe.
Which is the differerence between these characteristics?
4. Some characteristics are inherited and so passed on to the next generation
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
“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.
French biologist Jean Baptiste Lamarck (1744–1829)
“The inheritance of acquired characteristics”
4. Some characteristics are inherited and so passed on to the next generation
ObservationsObservations:
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?
Describe what's happening in these pictures..............
Pigeon and sparrow
Polar bears
Spider and fly
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.
Male African lionSilverback mountain gorilla
Survival of the fittestThe 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.
These ideas formed the basis of Darwin’s theory of evolution by natural selection.
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.
English naturalist, explorer, geographer, anthropologist, and biologist Alfred Russel Wallace (1823 –1913)
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 andblue, 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?