Final Exam Flashcards
When was the Cambrian explosion? and why is this time significant?
570 million years ago. This is when multi-cellular life takes off and all major body plans of animals are established.
When was the Burgess shale formed?
540 million years ago.
Why is the Burgess shale significant?
1) Some of the best fossil preservation of soft bodied organisms. 2) Showed that complex life was present in earths early stages which defied the theories at the time.
Why is the fossil record significant?
It allows us to view evolutionary change over time and examine speciation and extinction.
What is a draw back to the fossil record?
Soft bodied organisms do not preserve as well as hard bodied ones so there are gaps in the history.
What is perpetual change?
One of Darwin’s theories that the living world is always changing with hereditary passed from past to present life.
What is evidence of perpetual change?
The fossil record because you can trace evolution and hereditary in it.
What is common Descent?
Another of Darwin’s 4 theories that states all forms of life came from a common ancestor through a branching of linegaes.
What is adaptive radiation?
The production of ecologically diverse species from a common ancestor.
What is evidence to support Darwin’s theory of common descent?
Homology, This is the idea that animals share similar structures despite diverse modifications. E.g humans and bats both have finger like structures. E.g bat wing, human arm and fin diagram.
What is homology?
The idea that animals share similar structures despite diverse modification.
What is Darwin’s theory about multiplication of species?
The idea that evolution creates new species by splitting older ones. Evidence of this is allopatric speciation where 1 species of a population is separated by a physical barrier and becomes 2 species (or more).
What is Ontogeny?
The history of the development of an organism. Similar to homology. E.g fish, human embryos look remarkably similer despite being very different spcies. Also helps to prove common descent.
How does natural selection occur?
It occurs because of genetic variation e.g some individuals will have weaker genes or defects that allows them to be selected against. Excess offspring are produced, this excess offspring forces competition.
What happens when natural selection occurs?
It creates new adaptions and can possibly create new species if conditions are right. ( Speciation).
What are RIMs?
Reproductive Isolating mechanisms.
What are the 2 types of RIMs?
Prezygotic and Postzygotic.
Give examples of prezygotic RIMs
Habitat, timing or temporal, behavioural and physical. Habitat: Animals live in different places. Temporal: animals are breeding at different times. Behavioural: Different breeding behaviour e.g different sound communication or courtship. Physical: The key doesn’t fit the lock, incompatable structures.
What is a postzygotic RIM?
Offspring are produced but zygotes are weak non-viable or sterile. E.g Tiger trout.
What is Gradualism?
Darwin’s theory that physical changes among species are small and accumulate over time rather then occuring in one generation. This has been partially proven but doesn’t fully explain all examples.
What is natural selection?
The idea that organisms accumulate favorable characteristics over time based on their Enviroment. (Adapations).
What is phyletic gradualism?
Darwin’s idea of gradualism describing slow gradual change on a geological time scale ( natural looking phylogenetic tree). Thought the be incorrect because it does not explain extincting events .
What is punctuated equilibrium?
Contradicts the phyletic gradualism model. It shows morphology changes as short bursted events followed by very long periods of little change.
What are the types of natural selection?
1) Directional: A shift in the mean population e.g light skinned slug is favored over dark and medium slugs. 2) Stabilizing selection e.g medium skinned slugs are selected for and dark and light skinned are selected aginst. 3) Disrupted selection light and dark skinned slugs are favored against medium skinned slugs.
What is sexual selection?
This is when traits are developed in order to be more competitive when selecting mates. There are male combat structures e.g antlers horns, they are costly but without them chance of reproduction is small. Female choice plays the other part males develop colors, calls etc to attract them but in turn makes them more easy targets for predators.
What is are adaptive radiations?
Speciation gone crazy e.g Darvin’s finches started as one species and became 14 species.
What was the permian extinction and when did it happen?
250 million years ago 90% of marine invert species went extinct.
when was the cretaceous extinction?
65 million years ago (Dinosaurs dead)
What is a consequence of mass extinctions?
It opens the door for massive adaptive radiations of the remaining organisms because there was vast amounts of ecological space avaliable to thrive.