Survival of the Fittest Flashcards
What is evolution?
Evolution is the gradual change in the genetic material of a population of organisms over a period of time.
Which scientist contributed most to the theory of evolution?
Charles Darwin
Where did his ideas about evolution originate?
On a science expedition around the world, The Galapagos Islands influenced Darwin’s theory the most.
What was another theory of evolution proposed by Lamarck?
The Inheritance of Acquired Characteristics (which thought that if an animal somehow altered a body structure, it would pass that change on to it’s offspring)
Give an example of Lamark’s theory.
He thought that when giraffes stretched their necks to reach high food it would make them longer, and these longer necks would be passed on to their offspring.
Why was Lamarck’s theory dismissed?
Animals physically changing through their life does not effect the DNA they pass on to their offspring.
Name another scientist who has similar ideas to Darwin.
Alfred Wallace
Explain what natural selection is
natural selection is the mechanism/process of evolution.
What other term is used to describe natural selection?
Survival of the fittest
Give examples of selection pressures
Predators, Change in environment, Disease, Competition for food, space, reproductive resources
Explain the process of natural selection.
- Variation already exists within a population
- A selection pressure acts on the population
- Individuals with the favourable trait will survive and reproduce passing on the genes for the favourable trait to the next generation
- Over time the population will therefore change
Why is variation important?
Variation creates the opportunity for species to adapt and better fit their environment, helping them survive and reproduce
What are the sources of variation?
DNA mutations
Gene flow
Sexual reproduction
(sources of variation) DNA mutation
Mutations are changes in an individual’s DNA. These can happen spontaneously and result in new proteins being made, and therefore new traits/variations emerging in an individual.
(sources of variation) Gene flow…
leads to genetic variation as new individuals with different gene combinations migrate into a populations
(sources of variation) Sexual reproduction…
promotes variable gene combinations in a population leading to genetic variation
Why is natural selection often called ‘survival of the fittest?
The theory of natural selection is about how organisms with the most helpful mutations for living in their environment are the ones who will survive and go on to reproduce.
Definition of species
A species consists of a group of living organisms that can exchange genes or breed together and produce fertile offspring.
Definition of speciation
The formation of new species as one species splits or evolves into new species is called speciation.
Isolating Mechanisms
Mechanical isolation: Different reproductive parts.
Behavioural isolation: Species in the same area are capable of breeding, but have differences in courtship rituals.
Ecological isolation: Species occupy different habitats.
Geographic isolation: Species separated by geographic barriers e.g. rivers or mountains.
Temporal isolation: Species reproduce at different times of the day or seasons.
Definition and examples of hybrids
The infertile offspring of genetically similar species eg. Liger, Zonkey, Pizzlies
What is extinction?
Extinction is the complete disappearance of a species when the last of its individuals dies off.
When does extinction occur?
Changes in the environment make the habitat so unsuitable that members of the species cannot reproduce.
A lack of genetic diversity places species under threat.
A new species that can outcompete other species for a niche occurs e.g. an alpha
Process of Speciation
- A population(s) of the same species becomes isolated by an isolating mechanism
- The isolated populations are exposed to different selection pressures
- Over time, enough differences accumulate in the two populations until they form new species and can no longer interbreed to produce fertile offspring.
Explain how convergent evolution occurs and what evidence there is to support it
occurs when unrelated organisms evolve similar adaptations in response to their similar environment.
Species that demonstrate convergent evolution typically have analogous structures
Explain how divergent evolution occurs and what evidence there is to support it
occurs when closely related species become more different over time due to different environmental conditions and different selection pressures.
Divergent evolution produces new species from a common ancestor.
Species that show divergent evolution have homologous structures
What are homologous structures and what do they indicate about two species? Know an example.
physical features with the same/similar structure but different functions. They indicate that two species have a recent common ancestor. Eg. pentadactyl limb (humans, horses, cats, bats, whales, etc.)
What are analogous structures and what do they indicate about two species? Know an example.
Physical features with the same/very similar functions but different structure. This indicates two species have had similar selection pressures. Eg. bird/butterfly wings.
What are vestigial organs? Name an example in humans and another species.
structures that were once used by our ancestors but have reduced in size and function due to the lack of selection pressure for them.
Eg. Wisdom teeth, snake’s pelvic bone.
Why do vestigial organs still exist?
Because they were not selected against
Explain how comparing nucleotides or amino acid sequences provides evidence of evolution between species.
nucleotide and amino acid sequences are both made of universal parts, when comparing sequences the more similar the sequence the more recent the species’ common ancestor was
How are modern humans classified?
mammals > primates > hominids > hominins
Common features of the skulls of hominins
The foramen magnum is towards the front which allowed the organism to walk up right. Thin-walled, high vaulted skull with a flat and near vertical forehead.
Common features of the skeletons of hominins
Pelvic bones are more bowl-shaped and the hipbone is shorter compared to chimp’s which helps facilitate bipedalism.
Name 5 hominin species in order of evolution.
Australopithecus afarensis, Homo habilis, Homo erectus, Homo neanderthalensis, and Homo sapiens
Which hominin species first used stone tools?
Homo habilis
Which hominin species first migrated out of Africa?
Homo erectus
What are fossils?
The preserved body, impression, or trace of a dead organisms.
What are the different types of fossils?
Cast fossils, Mold fossils, Trace fossils
Cast fossil
forms when a mold is filled in with sediment
Mold fossil
a fossilized, hollow impression of a plant or animal
Trace fossil
nests, eggs, tracks, coprolites (dinosaur poo), that have been fossilized.
Describe Darwin’s contribution to the theory of evolution.
Darwin’s theory of natural selection proposed that individuals best suited to their environment survive, passing on these favourable traits to their offspring, leading to evolution over time. This is the most popular and supported theory to this day.
Describe the difference between Darwin and Lamarck’s theories of evolution.
Lamark’s theory said that changes in an organism’s characteristics acquired during its life would be passed on to its offspring. While Darwin theorised that organisms are born with mutations they can pass on to their offspring.
How do new species evolve according to natural selection?
Speciation
How can biologists identify if two groups of organisms are the same species?
They can test whether or not the two groups of organisms can breed and produce fertile offspring.
Be able to explain how the larger brain capacity of Homo sapiens helped their survival.
Homo sapiens’ larger brain capacity allows them to develop more advanced survival strategies.
Know what bipedalism is and which structural features of hominins facilitate it.
Bipedalism means they walk erect on their hind legs.
Hominins’ foramen magnum being towards the front of their skull along with a more bowl-shaped pelvis and a shorter hip bone help facilitate bipedalism.
What is the difference between relative age and absolute age?
Relative age is an approximate age while absolute age is a calculated age and much more specific.
How is relative age established? Know how to read strata diagrams.
If the age of a fossil in another rock layer (or the rock layer itself) is known, an approximate age can be determined.
How is the exact (absolute age) determined?
Scientists can work out the more precise age of the fossil by using radioactive dating techniques.
What is meant by a radioisotope’s half-life?
The time taken for the concentration to fall to half of it s initial value.
Be able to calculate decay of a radioisotope (when given relevant information).
- Determine how many half lives have passed.
100g → 50g = 1 half life
50g → 25g = 2 half lives - Multiple the number of elapsed half lives by the specific half life of the radioisotope.
2 x 700 million = The fossil is 1.4 billion years old
