Evolution Flashcards
Define Species
A group of organisms with common characteristics that can interbreed with each other to produce fertile offspring.
Define Adaptation
A characteristic or a behaviour of a species that allows it to survive and reproduce more effectively in its environment.
Define Population
A group of organisms of one species that interbreed and live in the same place at the same time. Individuals of the same population generally have the same number and types of genes but different alleles (variations of the genes).
Define Environment
The surroundings or conditions in which an animal or plant lives or operates, including biotic and abiotic factors.
Types of adaptations
Structural adaptations relate to the size and shape of an organism and its various body parts, for example, a kangaroo’s powerful leg muscles assist it in hopping at high speeds.
Physiological adaptations relate to how an organism’s body works, for example, the skin cells of a chameleon change pigment production to alter the chameleon’s colour, which assists the chameleon to hide
Behavioural adaptations relate to an organism’s behaviours, for example, penguins huddling together to stay warm.
Example of allele varieties in a population
For example, all humans will have the gene for eye colour, but the alleles they have for this gene may be blue, brown or even hazel.
Define evolution
Evolution is the permanent gradual change in the genetic composition of a population over long periods of time due to natural selection. This can be observed as changes in allele frequencies in the gene pool (different versions of a gene) and phenotypes (physical traits) in a population. Mutations introduce new alleles into the gene pool.
Why does evolution occur?
Selection pressures cause these new phenotypes to survive or die out. If an organism displays traits that make it suited to its environment, then it is able to mate and produce offspring. The offspring will have the same survival characteristics (and alleles) as their parent. This gradually changes the frequency of alleles in the gene pool.
Define phenotype
an observable trait
What is the theory of evolution
Most species reproduce more young than can and do survive, because they exceed the resources (food,space,water and mate) required to sustain them.
This limits population sizes by creating competition within the species for the limited resources.
There is variation within the members of a species which is passed on.
Some traits are more favourable (i.e better adapted to the environment)giving the individual a competitive edge. This is natural selection.
Those individuals with favourable traits which make them better adapted to their environment will survive and are more likely to reproduce and pass on these favourable traits to their offspring thereby contributing more to the next generation than those that are less fit. This is known as survival of the fittest. In each generation more individuals will be found with the favourable traits, e.g. Peppered moths in England.
How did the public react to Darwin’s theory?
Drawn in 1871, it depicts Darwin himself as an ape. The cartoon reflects how many people felt about Darwin and his theory during his own time. Darwin had actually expected this type of reaction to his theory and had waited a long time before publishing his book for this reason. It was only when another scientist, named Alfred Russel Wallace, developed essentially the same theory of evolution that Darwin put his book into print.
Define hypothesis scientific law scientific theory scientific method
A suggested explanation for an observation that is followed with experimentation.
A basic fact that describes the behaviour of a natural phenomenon.
An explanation of an aspect of the natural world and universe that has been repeatedly tested and corroborated in accordance with the scientific method
The process of objectively establishing facts through testing and experimentation.
Evidence of evolution occurring examples
Palaeontology (The Fossil record)
Comparative anatomy (Homologous structures)
Comparative embryology
How does the fossil record support the theory of evolution?
Fossils provide evidence for the evolutionary change through now extinct forms that led to modern species. For example, there is a rich fossil record that shows the evolutionary transitions from horse ancestors to modern horses that document intermediate forms (transitional features) and a gradual adaptation of changing ecosystems.
Example of a species which gradually diverged into several species
During his journey, Darwin visited the Galapagos Islands, which are home to at least 13 species of finch. He noticed that the different finch species were similar in colour and size, but had variations in their beaks that made them suited to the food sources available on their particular island. Some used twigs to extract insect larvae from tree branches, some drank blood from seabirds, some removed ticks from tortoises, and some ate seeds, leaves and flowers. He proposed that all species of finches in the Galapagos were the descendants of one shared, ancestral species, a ground-dwelling, seed-eating finch, which had migrated out to all the islands from the mainland. Over many generations the different groups of finches had evolved to suit their different environments and feeding habits. The groups of finches are now so different from one another that they do not interbreed.They have become separate species.
Define fossil
The preserved remains, traces or imprints of dead organisms.
Define natural selection
The process by which individuals of a species that are better suited to their environment are more likely to survive and reproduce (while those not so well fitted to survive either die or fail to reproduce).
Can fossilisation occur anywhere?
If an organism is covered shortly after its death by dirt, mud, silt or lava the micro-organisms that cause the decay cannot work. This is because there is no oxygen therefore prohibiting the formation of apatite (requires oxygen to form).
How does fossilisation occur?
An organism dies and is quickly covered by sediment. Over time, the sediment turns into rock. The remains of the organism turn into a fossil. The fossil is flattened by layers of rock. The rock is folded and eroded and the fossil can be seen on the surface.
Define transitional fossil
Transitional fossils refer to fossils that have the characteristics of two different groups of organisms
Example of transitional fossil
Archaeopteryx is a well known example of a transitional fossil. This was a small flying dinosaur with feathers, its fossils are 150 million years old.It appeared in the late Jurassic and shared features with both birds and reptiles, suggesting that birds evolved from these reptiles.
REPTILE features: long-tail, claws, solid bones, teeth
BIRD features: wish-bone, feathers, attaches for flight muscles on the sternum (breast bone).
Define comparative anatomy
Comparative anatomy refers to the studies of similarities and differences in structure between different organisms.
Example of comparative anatomy between different groups of organisms
The forelimbs of amphibians, reptiles, birds, and mammals have similar structures but different functions. Frog (amphibian) uses its forelimb to raise the front of the body. Lizard (reptile) uses its forelimb for walking and running. Birds forelimbs are modified as wings for flying. Mammals use the fore limbs for grasping, walking, running, swimming, flying etc.
Define homologous structures
Refers to body parts of animals that have a similar structure or origin
