B15: Evolution Flashcards
Natural Selection
> The process by which evolution takes place.
Organisms produce more offspring than the environment can support so only those who are most suited to their environment will survive to breed and pass on their useful characteristics.
When were the first life forms developed on earth?
3 billion years ago.
Lamarck’s Theory
The way organisms behave affects the features of their bodies.
If a particular characteristic is useful to a species, it would grow and develop.
These changes would then be passed onto the offspring.
Darwin’s Thoery
Evolution takes place through Natural Selection.
4 Key steps to Natural Selection
> Mutation of Gene
Advantage to Survival
Breed
Pass on genes
What three types of animal did Darwin study?
Finches, Iguanas and Tortoises
Difference between evolution and natural selection
Natural selection is a PROCESS taking many generations.
Evolution is a THEORY of how species changed over millions of years.
Why was Darwin’s theory only gradually accepted?
> It conflicted with religious beliefs
Insufficient evidence
Didn’t have a mechanism for explaining inheritance and and variety, as genes weren’t discovered for another 50 years.
Why do mutations occur?
Through naturally occurring mistakes made in copying the DNA when the cells divide.
Evolution
The process of slow change in living organisms over long periods of time as those best adapted to survive breed successfully.
How do we classify organisms
By studying their similarities and differences.
A species
A group of organisms that can breed successfully to produce fertile offspring.
Evolutionary Tree
a model of the evolutionary relationships between different organisms based on their appearances, and increasingly, on DNA evidence.
Ways that fossils are formed
> From the hard parts of an animal.
When one or more of the conditions for decay are not present, e.g oxygen, bacteria.
When harder parts of the organism are replaced by minerals and become part of the rock.
How fossils are formed
- Animal dies and falls to ground.
- Flesh rots, but skeleton is covered by earth before it too can decay.
- Over millions of years, the skeleton becomes mineralised and turns to rock.
- The rocks shift in the earth with the fossil trapped inside.
- Eventually fossil emerges as earth shifts and erosion takes place.
Conditions that affect decay
> Temperature
Moisture Levels
Oxygen Levels
Presence of a decomposer.
Throughout history, how many species have existed?
4 Billion
Extinction
The permanent loss of all the members of a species.
What links all of the causes of extinction?
They all involve a changing in the environment of the organism.
What causes extinction
> New Predators > New Diseases > The introduction of new competitors. > Changes to the climate/ environment. > A single catastrophic event.
Geographical Isolation
When two populations become physically isolated by a geographical feature.
Endemic
When a species evolves in isolation and is found in only one place in the world.
Speciation
When two parts of a population of the same species evolve in different ways until they are unable to interbreed, thus creating a new species.
