Evolution

Frage	Antworten
Relative Age	Age of objects expressed in relative terms so that they are identified as younger or older than other objects, but the actual ages of the objects concerned are unknown
Absolute Age	Ages of objects, such as a rock or fossil, expressed in actual years.
Stratigraphic Method	The stratigraphic method of dating rocks gives the relative ages of rock strata and uses the principle of superposition.
Principle of Superposition	Method of determining the relative ages of rock strata based on the principle that relatively older strata lie below relatively younger strata
Principle of Correlation	Method of identifying rock strata in different locations as having the same relative age because of the presence of a particular index fossil.
Index Fossil	An animal fossil of a group that existed continuously during a particular geological time and can therefore be used to date the rock in which it is found. Index fossils are found chiefly in sedimentary rocks. They are an essential tool in stratigraphy for comparing the geological ages of sedimentary rock formations.
Radiometric Dating	Technique for obtaining the age of objects that depends on the known rate of decay of a radioactive parent isotope to a stable daughter product, such as potassium-argon dating.
Half Life	Period of time required for half the amount of an isotope originally present in a sample to decay to its stable daughter product.
Potassium-Argon Dating (K-Ar Dating)	Technique used for dating igneous rocks over a wide age range and based on the radioactive decay off a potassium isotope to argon.
Carbon-14 Dating	A radiometric method of dating carbon containing material up to about 60000 years old.
Electron Spin Resonance	Technique useful for dating objects buried 50,000 to 500, 000 years ago. Depends on the fact that when mineral containing objects (such as fossil teeth) are buried they are bombarded by natural radiation by the soil. This causes some of the electrons in the minerals to move to a higher energy level. The rate at which high energy electrons become trapped is determined by the background radiation- the longer the material has been buried, the greater the accumulation of high energy electrons.
Fossils	Evidence or remains of organisms that lived long ago.
Direct Evidence	Bones, Teeth, Leaves and Shells
Indirect Evidence	Footprints, tooth marks, tracks, burrows and coprolites
Trace Fossils	Indirect fossil evidence of past life, such as tracks
Fossilisation	Process of preserving parts of organisms that lived in the geological past. It needs rapid burial of dead organisms and oxygen poor conditions.
Homologous Strucutres	Refers to structures that have a similar basic pattern/ form/ structure even though they may serve different functions.
Analogous Structures	Refers to structures on different species that carry out similar functions but are not necessarily similar in basic structure. Derived from different ancestral structures
Comparative Embryology	- In all terrestrial vertebrates- reptile, birds and mammals- gill slits are not present; however, non-functional gill slits are seen in the early embryos of these vertebrates. - A tail is normally absent from a human foetus as a newborn baby; however, a human embryo at some stage shows a primitive tail. - The similar patterns of embryonic development of different vertebrates is evidence of their relationship by evolutionary descent
DNA Hybridisation	1. The DNA is extracted from cells of 2 species purified and cut into fragment. 2. The repeated sequences are removed, leaving the unique genetic information of the DNA gene sequences of the 2 species. 3. The DNA fragments of the 2 species are made single stranded, mixed and allowed to pair. Some pairing will occur between the single strands from the 2 species is more similar. 4. A measure of similarity is then obtained by heating the double stranded DNA. The temperature at which half become single stranded melting temperature indicated relatedness.
Molecular Clock Concept	The number of differences in the proteins of 2 species might indicate the time that had elapsed since these species diverged from their most recent common ancestor.
Comparative Genomics	Identifying and examining entire genomes in different species.
Divergent Evolution	Occurs when ancestral species (closely related) change over time to become more dissimilar (usually in response to different environmental conditions and selection pressures) to give rise to many new species, each occupying a different niche and showing adaptations to help survive and reproduce.
Adaptive Radiation	Is a special case of divergent evolution. It is the evolution of a variety of species, each adapted for life in a different niche and each evolved over time from a single ancestral species.
Convergent Evolution	Over geological time, natural selection may acct on distantly related species to produce superficial similarities that are not due to shared ancestry but reflect the fact that the species are adapted to a similar way of life.
Parallel Evolution	Two related species with a common evolutionary ancestor that have diverged and then evolved with structural similarities because of their similar way of life.
Co-Evolution	Refers to changes in 2 different species that have ac close interaction and are dependent on each other for their survival.
Speciation	The process by which new species are formed through natural selection acting on two or more populations that must be isolated in some way.
Habitat Isolation	Different variations in the group require different habitats such as forests, grassland
Seasonal Isolation	Groups have different breeding times so they may not be fertile at the same time.
Behavioural Isolation	Different courtship behaviours
Geographical Barriers	Physical barriers such as hills, rivers, countries separating, rise and fall of sea level
Mechanical Isolation	Where structural variation/ differences occur in the genital area.
Speciation In Detail	1. isolation of populations 2. Isolated populations accumulate genetic differences due to different selection pressures and genetic drift. 3. No gene flow between populations 4. Enough differences accumulate so that new species are unable to interbreed and produce viable and fertile offspring if come together again.
Phyletic Evolution	In which one population progressively changes over time to become a new species.
Branching Evolution	In which a population of one species splits and one part of the original population evolves separately to form a new species distinct from the original species.
Extinction	Where a particular species no longer exists or where a particular variation no longer exists (due to allele being eradicated)

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