exam revision - changes in biodiversity over time Flashcards
what is macroevolution
the term used to describe large scale changes, as viewed in the fossil record, involving whole groups of species and genera.
what is microevolution
describes the small scale changes within gene pools over generations
explain fossils in evidence of evolution
fossils are evidence of prehistoric life, fossils dont need to be a piece of the actual organism, but they can be traces of the organisms too (eg footprint). The fossil record is a geological time scale of fossils.
how do fossils form
an organism must die in a spot where sediment can form quickly over them, for example under water, sandstorm, volcanoes. This allows a layer of sediment to settle and prevent decay. Now the organism must lie undisturbed, an increase in pressure causes the sediment to form rock.
how can fossils be aged
stratigraphic correlation, radioisotopic dating
what is stratigraphic correlation
by calculating the age of various rock strata, and comparing this with fossil evidence in the rock it is possible to infer the age of the fossils and the physical actions occurring at the time.
what its radioisotopic dating of fossils
an isotope is one of several forms of a particular element. Isotopes follow definite chemical patterns, so they release certain amounts of energy over time that can be measured. Good example of this is Carbon 14 dating, is used to date fossils younger than 40,000 years. When an organism dies C14 begins to decay and becomes nitrogen instead (C12 stays the same) . It takes 5,730 years to change to N, this is called a half life. By comparing how much nitrogen to C12, we can work out the fossil age. Another example is potassium/ argon dating that can date fossils back to 100 million years
what are homologous structures
are anatomical features of different organisms that have similar appearance or functions that are inherited from a common ancestor.
what are analogous structures
types of homologous structures, but they have seperate evolutionary origins, but they are superficially similar because they evolved to serve the same function.
what are vestigial organs
organs are identified which have lost their functions. They indicate relationship with their ancestors.
what are types of evolution
divergent evolution, convergent evolution, parallel evolution.
what is divergent evolution
is the evolutionary pattern where two species gradually become increasingly different. It occurs when closely related species diversify to new habitats.
what is convergent evolution
takes place when species of different ancestry begin to share analogous traits because of a shared environment or other selection pressures.
what is a phylogeny tree
are diagrams that show evolutionary pathways of species. These pathways or relationships are inferred and are based on evolutionary evidence such as fossils, DNA hybridisation or anatomical comparisons. They usually have a time scale and can show extinct species.
what is a cladogram
another type of phylogenic tree, however they tend to indicate the evolutionary relationship between species, based on specific characteristics
what is a molecular clock (homology)
it is known that the more closely related a species, the more similar there DNA sequences. A molecular clock uses the number of changes in a DNA series between two possibly related species. Based on the idea that mutations occur in regular time spans. By assuming this it is possible to calculate more accurately when a species may have diverged.
what is mitochondrial DNA
is a small circular DNA located in the mitochondria, and is inherited strictly from mother to child. Normally our mtDNA is identical to our mother, but mtDNA mutates occasionally so that a base changes. Because of these mutations, human mtDNA has slowly diverged from that of mitochondrial eve, and the amount of mutation is roughly proportional to the time that has passed. This means that similarity between mtDNA fro any two humans provides a rough estimate of how closely they are related.
what is DNA hybridisation
discovers the degree of relatedness between two species by examining how similar their base pair sequences are. Because DNA is a molecule of heredity, evolutionary changes will be reflected in changes in the base pairs in DNA.
Hybridisation of DNA is accomplished by heating strands of DNA from two species to 86 degrees which breaks the hydrogen bonds between all complementary base pairs. The resulting single stranded DNA are mixed together and cooled slowly, allowing similar strands of DNA from both species to begin to chemically join together or re anneal at complementary base pairs by reforming hydrogen bonds.
The temperature at which hybrid DNA separation occurs is related to the number of hydrogen bonds formed between complementary base pairs, if two species are closely related, most base pairs will be complimentary and the temperature of separation will be close to 86, but if the species are not related closely, they will not share many DNA complementary bases and the temperature of separation will be less than 86 as less energy is required to break fewer hydrogen bonds.
define hominoid
refers to members of the superfamily hominoidea, both present and past. Today it comprises of humans, gibbons, great apes, orang-utan, chimps, gorilla.
define hominid
the group consisting of all modern and extinct great apes
define hominin
the group consisting of modern humans, extinct human species and all our immediate ancestors
what characteristics do primates have in common
opposable thumbs, hands and feet can grasp, fingernails instead of claws, flattened face resulting in two eyes next to each other pointing in the same direction
what are examples of human advances
larger brains, different shape skull (flatter face rather than face projecting forwards, shows more emotion), bipedal gait (human adults walk most naturally on two legs), more advanced use of hands (humans can produce finely detailed objects by hand), more advanced forms of communication (spoken languages, sing language, gestures, music, written)
advantages of bipedalism
when Africa became dryer and the forest became a wooden savannah, it forced some apes/ early hominins out of the trees in search for alternate food sources. This meant hominins were scavengers, the advantage being they collected food and carried it to a home base. Freeing up of hands allows for development of tools and weapons, specialisation of tasks done by hand improved social interaction and cultural evolution. Being able to see over grass helps to spot predators and locate food sources.
what is a way of telling whether an early ancestor was bipedal or not
there is a hole in the base of the spine called the foramen magnum, which is the spot where the spinal cord enters the brain. The position of this indicates whether the individual had an upright stature or not, and therefore can determine when ancestors became bipedal.
what are the three types of evolution that have driven the development of humans
biological evolution, cultural evolution, technological evolution
what is biological evolution
where nature very slowly adapt us physically to our changing environment
what is cultural evolution
is how people adapt their behaviour to the environment. since these are conscious rather than totally random changes, they occur at a much faster pace than biological change
what is technological evolution
enables people to adapt or change their environment to meet their needs. This is often something that can be done without immediately changing cultural norms. Therefore it tends to happen at a much faster rate than cultural change.
what are theories of human distribution
multiregional continuity model, out of Africa model
what is the multiregional continuity model
states that after homo Erectus left Africa and dispersed into other portions of the old world, regional populations slowly evolved due to natural selection.
what is the out of Africa model
asserts that modern humans evolved relatively recently in Africa, migrated into Eurasia and replaced all populations which had descended from Homo Erectus.
