topic 1 - origin of the species

Nicolaus Steno

Found fossils, fossilised teeth from ancient sharks. Some of these were found on mountains, seas, must have covered parts of the Earth in the past.

Mary Anning

Mary identified unusual fossils, unusual fossils in the South of England that did not represent any living creatures. Her findings suggested animal species could go extinct, which was controversial at the time

Jean-Baptiste Lamarck

One of the first individuals to recognise species were not fixed: they could change

Theory rejected: theory that living beings acquired characteristics in their lifetime and adapted to their enviornment. Like giraffes extending their necks to eat tall trees. Lacked scientific foundation without experimental evidence

Charles Darwin

Accumulated extensive evidence to support his idea that evolution was shaped by the process of natural selection. Collected many specimens, including birds from the Galápagos Islands, which had vastly different beak shapes

Theory was going to create a stir, so gathered as much information as possible

Darwin’s three propositions

Species are not immutable: populations show phenotypic variation and species can change over time

Descent with modification: related species, which share a common ancestor, diverge from one another gradually over time (Bats use their wings to fly, seals use flippers to swim and human arms perform may tasks - bones that make up these structures show similarities)

Natural selection: differences in the phenotypes of individuals cause some of them to survive and reproduce more effectively than others and therefore outcompete them.

Thomas Malthus

Predicted that the human population would grow so large there would not be sufficient food supplies. This would cause a fight for survival.

Natural selection

Evolution defined

The cumulative change in the genetic composition of a population or species over time

If a population showed no phenotypic variation

If population showed no phenotypic variation, no natural selection can occur if there is no variation. If food sources change, none of the finches would have a beak size suited to the new food, so could starve potentially causing extinction of species.

Speciation

Speciation is an evolutionary consequences of reproductive isolation.

Microevolution

Macroevolition

Paraphyly

Paraphyletic group includes the common ancestor, but not all descendants

Polyphyly

Polyphyletic group does not include the common ancestor

Monophyly

Monophyletic group includes the common ancestor and all descendants (a “clade”)