EVOLUTION GCSE Biology By Dr H E Bloomfield

Life began on Earth more than 3 billion years ago. A scientist called Charles Darwin suggested that all species of living things developed or evolved from these very simple life forms by a process called natural selection. EVOLUTION

Other theories for evolution had also been suggested including one by a Frenchman called Jean-Baptiste Lamarck EVOLUTION Lamarck suggested that any changes which occurred in an organism during its lifetime could be inherited.

So, if a giraffe needed to reach leaves high up in a tree and if it kept stretching up for these leaves, then its neck might get stronger and longer. Lamarck’s Theory

 This longer and stronger neck would then be passed on to its offspring.  This will lead to gradual change as the species becomes more perfectly adapted to its environment.

Lamarck’s Theory But we now know that changes that occur during an organism’s life are not usually passed on. Are tattoos / scars / dyed hair passed from human parents to their babies?

Charles Darwin had a different idea. He developed his theory of natural selection after he had been on a round-the-world trip and seen the huge variety of animals and plants that existed. Charles Darwin

Voyage on HMS Beagle to South America and the Galapagos Islands

Galapagos Islands

As Darwin sailed round these islands, he noticed the Finches had different beak shapes.

Darwin’s Finches

 The members of a species are not identical. They vary because of differences in their genes.  Individuals with the characteristics most suited to their environment are more likely to survive and breed successfully. According to Darwin’s Theory of Natural Selection

 The survivors will then pass on their favourable genes to the next generation.  Eventually over time, species will change (or Evolve) due to this Natural Selection process. According to Darwin’s Theory of Natural Selection

Darwin’s Theory of Natural Selection

Comparing Lamarck’s and Darwin’s Ideas

Darwin published his theories in a book The Origin of Species in 1859

Darwin’s theory of evolution by natural selection was only gradually accepted because The theory challenged the idea that God made all the animals and plants that live on Earth

In the 19 th century, people were much more religious and many were unhappy because Darwin’s theories of Natural Selection and Evolution contradicted the Bible. According to the book of Genesis, God created all living things in their present form. Darwinism and Religion

The media were quick to point out that Darwin was implying that humans had evolved from monkeys

‘Descended from the apes! My dear, let us hope that it is not true, but if it is, let us pray that it will not become generally known.’ Wife of the Bishop of Worcester (June 1860)

Darwin theory of evolution by natural selection was only gradually accepted because The theory challenged the idea that God made all the animals and plants that live on Earth There was not enough evidence at the time the theory was published to convince many scientists.

People had not discovered as many fossils and did not understand fully that they show how species had changed over time

Formation of Fossils

Formation of Fossils - Ammonites

Fossil of an ancestor of modern birds Trilobite

Evolution usually occurs over a long time – many thousands or millions of years (eg horses)

BUT, if new forms of a gene are created by mutation, there may be relatively rapid change in a species if the environment changes (eg peppered moths)

Darwin theory of evolution by natural selection was only gradually accepted because The theory challenged the idea that God made all the animals and plants that live on Earth There was not enough evidence at the time the theory was published to convince many scientists People had not yet discovered genes or chromosomes or how they were inherited. It was not until 50 years later that this was known.

Studying the similarities and differences between living organisms allows us to classify living organisms into animals, plants and micro-organisms. helps us to understand evolutionary and ecological relationships.

Models (eg evolutionary trees) allow us to suggest relationships between organisms.

Comparing Mechanisms of Evolution Cheetahs can run faster than 60 miles per hour when in pursuit of prey. How would an evolutionary biologist explain how this ability evolved, assuming their ancestors could only run 20 miles per hour? Wading birds have long legs and large feet. How would an evolutionary biologist explain this assuming their ancestors had smaller legs and feet?

Type A lives on an island where there is a lot of vegetation, such as grasses, on the ground. Type B lives on a different island where there is more bare soil and the vegetation, such as bushes, is far taller. Describe two features, that you can see in type B, that help it to survive where there is tall vegetation. Evolution of Giant TortoisesA B

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