04/12/12 Miss RadfordSurviving Change & Theories of Evolution

why do organisms evolve and what evidence is there for evolution?

WAL:

All

Most

Some

• Can you define the terms ‘Natural Selection’ and ‘Survival of the fittest’?

• Can you describe the time scales of evolution with evidence to support the theory?

• Can you compare and contrast two theories of evolution?

Starter question “What does the word evolution mean to you?”

What does “evolution” mean to you?

Evolution is how species have evolved from simple

life forms

Why do organisms evolve?

• All organisms want to survive to pass on their genes to their offspring.

• Random mutations may occur - leading to an advantageous characteristic (enhancing survival).

• And/or one or more selection pressures (e.g predators, food, territory/climate) act on the organism…

• All of these lead to what is known asNatural Selection and Survival of the Fittest.

Theories of Evolution• Lamarck believed in

acquired characteristics.

• The characteristics that help that organism to survive are passed to their offspring.

• So if your parents are body builders then you are born that way.

Another idea to explain evolution...

• Jean Baptiste Lamarck thought that animals evolved through ‘inheritance of acquired characteristics’

Theories of Evolution

• Darwin set out in 1831 on a voyage.

• At the Galapagos islands he saw different features on a variety of finches (we’ll come back to these later).

Theories of Evolution

• It was while Darwin was making observations of these finches, he came up with his theory of Natural Selection based on survival of the fittest.

Survival of the fittest

• Only offspring with the genes that best suit their habitat will stay alive and breed.

• This is natural selection.

• Only offspring with the genes that best suit their habitat will stay alive and breed.

• This is natural selection.

Survival of the fittest

Examples of selection pressures which

demonstrate natural selection and survival of the

fittest…

Predators

• The dodo was a flightless bird.

• New predators arrived on shore and they could not escape.

Environmental changes

• Scientists believe a big climate change caused dinosaurs to become extinct due to a meteorite crashing into the earth.

Competition

• A mutation can give one animal an advantage over another.

• Or sometimes one species can not compete with another as they are better adapted to their environment, causing extinction.

Diseases

• Diseases can wipe out a whole species quickly when the population live close together.

Survival of the fittest

Survival of the fittest

Why are the orange beetles more fit to survive than the green beetles?

Evidence to support the Theory of Evolution

• Darwin set out in 1831 on a voyage.

• At the Galapagos islands he saw different features on a variety of finches (told you we’d come back to them!)

The islands

To Do:

• “Darwin’s Finches”• You are going to use

different forceps as “beaks” to model each of the different finches.

• Record your results in the table provided.

• Answer the questions on the back of the sheet.

15 minutes

In your book:• Match the beak to its

adaptation (Match letter to number)

• What type of bird do you think each of these beaks belong to?

1) Strong & hooked beak for tearing fish2) Strong & nut-cracker like beak to grab and crush fruit & nuts3) Thin beak to reach nectar in flowers4) Chisel like beak to drill holes in trees and eat the insects within5) Pouched net like beak to scoop up fish

AB

EC

D

How did all these birds come to have different beaks??

Theories of Evolution

Fossils are also evidence to show natural selection in action

•A fast runner on hard ground•It has one toe forming a hoof

•Looks more like the modern horse with one hoof

•Slightly bigger•Walks mainly on one toe

•Has 3 toes on the ground•To run faster on drier ground

•Small•Lives on swampy land•Toes are well spread

•3 million years ago

• 7 million years ago

•25 million years ago

•60 million years ago

How long has it taken for the modern horse to evolve from its

ancestor – eohippus?

•3 million years ago

• 7 million years ago

•25 million years ago

•60 million years ago

60 million – 3 million = 53 million years!

To Do:• Complete the table provided by matching up the correct reason

why to support each evolutionary theory.

10 minutes

a struggle for existence means that individuals of the same species compete with each other

because of variations and differences in genes

individuals with characteristics most suited to their environment are more likely to survive and breed

the genes that enabled the parents to survive are passed on to the offspring

to ensure that new young survive and live each year, the continuation of the species

Theories of Evolution & EvidenceEvolution theory Reason why?

organisms produce large numbers of offspring

variation between individuals of the same

species

predation, disease and competition cause many

individuals to die

survival of the fittest

genes for survival are passed on

to ensure that new young survive and live each year, the continuation of the species

because of variations and differences in genes

a struggle for existence means that individuals of the same species compete with each other

individuals with characteristics most suited to their environment are more likely to survive and breed

the genes that enabled the parents to survive are passed on to the offspring

Fatboy Slim – Right here, Right now

1. What did the video show?2. Was this a good example of Evolution?3. What was wrong with what was shown in the

video?4. Did the video show “survival of the fittest”?

Home learning due:

• “Darwin Vs Larmark, Natural Selection and Darwin’s tree of life”

• Answer the questions on the sheet.

• You may write on the sheet or answer the questions in your book.

• Remember to use full sentences