- Born: England, 12/2/1809
- In October 1825, at the age of 16, Edinburgh
university
- 1827 - a student at Christ’s College in
Cambridge. His father wanted him to become a doctor but blood made Darwin
queasy, so he studied natural history.
- December 27, 1831: Darwin
was the ships naturalist aboard HMS Beagle – a five-year voyage around the
world visiting several continents
- During his travels, Darwin saw far more
diversity than he saw in his native county.
- numerous observations made while collecting
evidence that lead to his hypothesis about the way life changes over time.
- Darwin was intrigued by the fact that so many
plants and animals seemed remarkably well suited to whatever environment they
inhabited.
- He was
impressed by the ways in which organisms survive and produced their offspring.
- He was
puzzled by where different species lived and did not live.
- Of all the destinations that Darwin went to the
most influential was The Galapagos
Islands of the coast of South America.
- Although
they were all close together each had different climates and different species
that varied between them.
- In the Galapagos Islands Darwin studied
Tortoises and noticed that in different islands turtles had different shells.
- Darwin also noted the several different types of
birds on the islands. He thought the difference existed because of the
environments they lived in.
- While returning from his expedition, Darwin spent a great deal of
time analysing his findings. Darwin observed that :-
- the characteristics of many animals and plants
varied noticeably among the different islands of Galapagos.
- He
thought that animals living on different islands had once been members of the
same species.
- These birds all had different beak sizes and
shapes related to the diet and foods they were eating.
- Darwin thought that when these birds arrived on
the Galapogos islands, they all went and dispersed to different environments
where they had to adapt to different
conditions. =========è
over many generations, anatomical changes were made to allow them to obtain food and survive to reproduce.
- Darwin didn’t rush to publish his findings.
- In 1858 Alfred Russel Wallace wrote to Darwin
about a theory of evolution that was similar to his ideas, Darwin now had an
incentive to publish his findings.
The work of Jean-Baptiste Lamarck, Charles Darwin and Alfred
Wallace
Lamarck
Lamarck’s theory had 3 aspects to it:
Lamarck’s theory had 3 aspects to it:
- Tendency toward perfection- organisms change and have features that help them live better. Eg.
birds that needed to fly grew wings so they were better able to fly.
- Use and disuse-Organisms who use the body parts increasingly, will develop that part
better. The parts/featurees that are not used will disappear. Eg.. reptiles
stopped using their legs and evolved into snakes.
- Evolution of Acquired Traits-Organisms that change a favourable characteristic
will pass that change on to its
offspring.
- the giraffe stretches its neck to reach food high in
trees
- the giraffe's neck will get longer because it's used a lot
the giraffe's offspring inherit its long neck
- This theory
is wrong
Lamarck’s theory was not accepted because:
- acquired characteristics did not have a
genetic basis
- Lamarck thought simple organisms disappear
- However, Darwin could explain the
continued presence of simple organisms
Darwin stated that: - Giraffes that already have long necks survive
better
- Leave more offspring who inherit their long
necks
- à
variation
- Selection and survival
- Reproduction and inheritance of more fit traits.
- This theory
is wrong
Darwin’s theory
He explained his ideas on evolution in a book called On the Origin of Species, published in 1859.
Outline the steps that natural selection proposes:
VARIATION: individuals in a population have differences of their characteristics
OVERPOPULATION: leads to lack of resources needed for life.
COMPETITION: individuals compete for limited resources. Fighting for your resources, have to struggle to exist. Species unable to compete successfully eventually become extinct.
SURVIVAL OF THE FITTEST: individuals with characteristics best suited to their environment are more likely to survive
PASSING ON YOUR GENES: those with “fit” genes reach reproductive age and pass their genes and successful' characteristics onto their offspring.
1. a giraffe with a longer neck can reach food high up
2. a giraffe is more likely to get enough food to survive to reproduce
3. a giraffe's offspring inherit its long neck
He explained his ideas on evolution in a book called On the Origin of Species, published in 1859.
Outline the steps that natural selection proposes:
- Darwin’s principles for evolutionary change: Natural selection
- 6 main principles
- Variation: all unique individuals
have variations in their phenotypes (behaviour, body, chemistry)
- Heredity: some of
these variations will be passed onto their offspring
- Overproduction: more
offspring are produced than can survive.
- Limited resources: such as
food habitat or mates affect survival and reproduction
- Fitness: individuals
with favourable traits will have an advantage in their environment to survive
and are able to reproduce and pass on
their traits to offspring
- Genetic composition: these new
traits are passed on to the future generations with an increase frequency
VARIATION: individuals in a population have differences of their characteristics
OVERPOPULATION: leads to lack of resources needed for life.
COMPETITION: individuals compete for limited resources. Fighting for your resources, have to struggle to exist. Species unable to compete successfully eventually become extinct.
SURVIVAL OF THE FITTEST: individuals with characteristics best suited to their environment are more likely to survive
PASSING ON YOUR GENES: those with “fit” genes reach reproductive age and pass their genes and successful' characteristics onto their offspring.
- Overtime, natural selection results in
changes in the inherited characteristics of a population. These changes
increase a species fitness in its environment.
1. a giraffe with a longer neck can reach food high up
2. a giraffe is more likely to get enough food to survive to reproduce
3. a giraffe's offspring inherit its long neck
SELECTION PRESSURE:
DEFINITION: factors that determine which variations provide the organism with an increased chance of survival and have an advantage over the others.
2 FACTORS INFLUENCE SURVIVAL OF ORGANISMS:
1. BIOTIC (LIVING THINGS)
2. ABIOTIC (NON LIVING THINGS)
These factors have a role in determining which variations will give the organism an increased chance of surviving and have an advantage over the others = SELECTIVE PRESSURES
These factors are called selective pressures or selective agents. These pressures allow the organism to evolve and have more of its variation prevalent.
Selection pressure can come from anything.:
Examples of Selection Pressure
DEFINITION: factors that determine which variations provide the organism with an increased chance of survival and have an advantage over the others.
2 FACTORS INFLUENCE SURVIVAL OF ORGANISMS:
1. BIOTIC (LIVING THINGS)
2. ABIOTIC (NON LIVING THINGS)
These factors have a role in determining which variations will give the organism an increased chance of surviving and have an advantage over the others = SELECTIVE PRESSURES
These factors are called selective pressures or selective agents. These pressures allow the organism to evolve and have more of its variation prevalent.
Selection pressure can come from anything.:
- It has
to be consistent over a long period of time.
- It also
affects the reproduction or survival rates of a species.
- Availability
of prey/food - variants
with adaptations that allow them to obtain food have more offspring, eg
camouflage for stealth, weapons for killing prey or obtaining food, speed,
senses for finding prey/food.
- Presence
of predators – variants with adaptations to escape predators
have more offspring eg speed, camouflage.
- Environmental
stresses –ability to survive new climate best will have more offspring eg. Change
in climate caused by migration to another place
- Competition
with other species – humans and other members of a species
- Mates – variants
with adaptations allowing them to
attract a mate to have offspring eg. Strength, attractive, good provider
- For
example , if a predator eats old animals who can’t reproduce anymore, then this
doesn’t impact on the evolution of this species.(survival).
- Colour
also affects an organism’s chance of survival.
Insects that are camouflaged in their environment will be less seen by predators eg birds.
This will increase the chances of that insect’s population to reproduce.
If the insect was a different colour and could be seen, then its chance of survival and reproduction are limited and that species could become extinct.
Examples of Selection Pressure
- the peppered moth
- was mainly light coloured in the 19th
century.
- rested on tree trunks that were light in colour
because of the light coloured lichens growing on there
- the industrial revolution produced soot that
covered these trunks and made them dark.
- A dark moth evolved over time so it could be better
camouflaged
2. human influence to control organisms
- Has resulted in a selection pressure leading to new
forms of resistant insects that are not affected by the insecticide to evolve.
- Human influence by over using antibiotics
-The overuse of antibiotics to kill disease causing bacteria has led to the development of some bacterial strains that are resistant to many of the antibiotics used.
-hospitals reporting increased incidence of "multi resistant bacteria." These are bacteria that have evolved to become resistant to the effects of the antibiotics and as a result are effectively untreatable. These include strains of particularly dangerous bacteria such as Staphylococcus Aureaus (Golden Staph) that have the potential to be fatal.
Survival of the fittest
- An important factor for life is how well an
organism is in its environment
- Darwin named the ability of an organism to
survive and reproduce in its environment fitness
- Darwin purposed that fitness is the result of
adaptations.
- Any characteristic that increases the chance of
survival
- Adaptations can be:
- Anatomical- speed, protection, camouflage
- Physiological- the way it goes through synthesis
- Behavioural- the way it hunts
- Anatomical- speed, protection, camouflage
- Individuals with low levels of fitness die and do not reproduce, and those
with high levels of fitness survive
and reproduce successfully.
- He call this process “survival of the fittest”
Survival of the fittest VS Natural selection
* survival of the fittest is the process of natural selection that creates evolutionary change. Fitness in biology means the ability of an organism to survive AND reproduce in their environment.
* natural selection gives individuals that are better adapted to their environment an advantage over those who are not. The advantage relates to survival and reproductive success.
* survival of the fittest is the process of natural selection that creates evolutionary change. Fitness in biology means the ability of an organism to survive AND reproduce in their environment.
* natural selection gives individuals that are better adapted to their environment an advantage over those who are not. The advantage relates to survival and reproductive success.
Natural selection occurring in rock pocket mice
- Rock pocket mice live in the deserts of south
west America
- Original mice had light-coloured coats that
blended with the rocks and sandy soil protecting them from their owl predators.
- Around 1.7 million years ago, volcanic eruptions
spewed out wide trails of black lava that wove right through the middle of
pocket- mouse territory.
- To this day there are two different types of
pocket mice
- Light coloured mice living in the sandy soil
- Dark coloured mice that live on the black lava
- The black mice came about through the process of
evolution.
- A natural mutation of the colour gene made the
mice have dark fur
- The dark mice have the advantage over the white
mice over their predators
- This makes it able for them to survive and pass
on their genes to their off spring
- Whenever a favourable variation occurs, it can
quickly become the major form in a population
- Every year mice produce more offspring that are
able to reach adult hood and pass on their genes.
- Thanks to natural selection the offspring with
favourable characteristics are more likely to survive and reproduce.
- Variation-
A mutation for a black fur occurs that has completely different characteristics
to other mice.
- Overpopulation-
there is now a lack of resources for these mice to survive on and there is in
danger because some are more prone to be taken as prey.
- Conflict- The mice are fighting for
their resource. Some are struggling to survive because they do not blend in
with the black lava rock.
- Survival
of the fittest- The black mice have the fitter genes and are more likely to
survive from their predators and be able to pass on their genes.
- Passing
on of fit genes- The mice with the fit genes are able to survive till
adulthood where they are able to pass on those genes to their children. The new
mice would be more likely to survive because they have dark fur and have fitter
genes.