Topic 5 Flashcards
What can occur if there is variation among the same species?
Natural selection
Variation
- typical populations may vary in many aspects
- variation in humans is obvious ie hair colour, height
- with many species the variation may not be obvious
- needed for natural selection
What causes variation?
-Meiosis, mutation and sexual reproduction
Why is mutation a source of variation?
New alleles are produced which increases the gene pool
Why is meiosis a source of variation?
Why is sexual reproduction a source of variation?
- involves the fusion of male and female gametes.
- The gametes usually come from different parents, so the offspring has a combination from two individuals
What is the only source of variation for species that do not undergo sexual reproduction?
Mutation
Adaptation
- characteristics that make an organism better suited to life
- develop by natural selection
- do not develop during the lifetime of one individual
Overproduction
- when species produce more offspring than the environment can support
- lead to struggle for resistance as there will be a competiton for resources
Differential survival and reproduction
- Individuals that are better suited to survive produce more offspring while those who are less adapted die or produce less
- natural selection
- Giraffes with longer necks are better suited to survive
What is heritable?
When the variation can be passed on
When does evolution occur?
When the heritable characteristics of a species change
What is another definition for biological evolution?
A change in the allele frequency of a population’s gene pool over successive generations
What provides evidence for evolution?
-Selective bredding of animals by artifical selection and fossil records
Fossils
-preserved reamins of an organism
- revealing features of an ancestor to compare with living descendants
- can provide direct evidence of ancestoral forms
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Describe the law of fossil succession
- fossils are dated by determining the age of the layer they are found
- lower layers are older and higher layers are above
- can be used to indicate a sequence of movement as prokaryotes appear in the fossil record before eukaryotes
- and ferns appear before flowering plants
What do archaeopteryx link together?
An example of a transitional fossil is archaeopteryx, which links the evolution of dinosaurs (jaws, claws) to birds (feathers)
What is selective breeding a form of?
Artifical selection
Describe the process of selective breeding
- breeding members of a species with a desired trait thus making the frequency more common
- ## targeted breeds can show variation in a very small time
What 3 animals are commonly domesticatdly bred?
- Horse, cow , dog
Give an example of selective breeding?
Greyhounds ( racing dogs) were breed to be sleak and fast to race
What are homologus structures?
Anatomical features that are similar in basic structure despite being used in different ways
Adaptive radiation
Comparison of the pentadactyl limb of mammals, birds, amphibians & reptiles
- Pentadactyl limb has 5 fingers
- Human hands are adapted for tool manipulation (power vs precision grip)
- Bird and bat wings are adapted for flying
- Horse hooves are adapted for galloping
- Whale and dolphin fins are adapted for swimming
What does continuous variation match?
Gradual divergence
Continuous variation
- within a population there will be genetic variation
- normally follows a normal distribution curve
- if two populations are separated they may experience different conditions and will overtime adapt to those said conditions and gradually diverge from one another
- the degree of the divergence will depend on the amount of time separated and the extent of the separation as populations in close proximity = less variation
What is speciation?
- the process by which two related populations can diverge into separate species by evolution
- the populations may diverge to a point where they can no longer interbreed to produce fertile offspring
What are the features of bryophyta?
- reproduce by releasing spores
- mosses, liverworts
- no xylem or phloem
- no true roots – rhizoids
What are the features of filicinophyta?
- have leaves, roots and stems
- have xylem and phloem
- ferns
- reproduce by releasing spores from clusters
What are the features of coniferophyta?
- confiers
- have leaves roots and stems
- have xylem and phloem
- reproduce by seeds
What are the features of angiospermaphyta?
- have roots, stems and leaves
- have xylem and phloem
- all floweing plants and grass
- reproduce by seeds in fruits
