5.1 Evolution Evidence Flashcards
what is biological evolution?
cumulative change that occurs within a population between one generation and the next
how are heritable characteristics encoded?
by genes and may be transferred between generations as alleles
what is a concise definition of biological evolution?
a change in the allele frequency of a population’s gene pool over successive generations
what do fossil records provide?
evidence by revealing the features of an ancestor for comparison against living descendants
what is a fossil?
preserved remains or traces of any organism from the remote past
what two ways do fossils provide evidence for ancestral forms?
direct - bones, teeth, shells, leaves etc
indirect - footprints, tooth marks, burrows and faeces
what is the fossil record?
the totality of fossils both discovered and undiscovered
(shows that over time changes have occurred in the features of living organisms)
how can fossils be dated? (3)
- by determining the age of the rock layer which the fossil is found
- sedimentary rock layers develop in chronicle order, so low layers are older and newer strata from on top
- each strata represents a variable length of time that is classifieds according to geological time scale)
In what order are different kinds of organisms found in rock layers? (3)
- prokaryotes before eukaryotes
- ferns before flowing plants
- invertebrates appear before vertebrates
what is the law of fossil succession?
newer species likely evolved as a result of changes to ancestral species
why is the fossil record incomplete? (2)
- fossilisation requires unusual set of specific circumstances in order to occur so very few organisms became fossils
- only the hard parts of an organism is typically preserved, so only fragments of remains are discovered
what are transitional fossils?
they demonstrate the intermediary forms that occurred over the evolutionary pathway taken by a single genus
how do transitional fossils work?
- they establish links between species by exhibiting traits common to both an ancestor and its predicted descendants
what is an example of a transitional fossil?
- archaeopteryx, links the evolution of dinosaurs to birds
what is an example of how fossils provide evidence? (3)
comparing hominin skeletons
- Australopithecus is an early hominin ancestor that first appeared in fossil record 4 million yrs ago
- comparing these fossils to bone structure of modern man demonstrates evolutionary change
what is selective breeding?
form of artificial selection to produce desired traits in offspring
how does artificial selection work? (3)
- by breeding members of a species with a desired trait
- the trait’s frequency becomes more common in successive generation
- selective breeding provides evidence of evolution as targeted variation in a short period
what has selective breeding caused?
- allowed for the generation of new types of foods that has been bred to produce different foods by modifying plant sections through artificial selection
(eg. broccoli, cabbage and kale)
what are 2 examples of horse selective breeding?
- race horses - for speed and leaner, lighter, taller and quicker
- draft horses - for power and endurance and are sturdier and stokier
what are 2 examples of cow breeding?
- improve milk production
- Belgium blue - produce more edible lean meat
what are 4 examples of dog breeding?
- hunting dogs - smaller to enter fox holes
- herding dogs - heightened intelligence
- racing dogs - sleek and fast
- toy dogs - diminutive size
what may the comparative anatomy of groups show? (3)
- certain structural features are similar implying common ancestry
- anatomical features are similar in basic structure despite being used in different ways (homologous structures)
- the more similar homologous structures the more likely the more closely related
what do homologous structures show? (2)
adaptive radiation
- where several new species rapidly diversity from an ancestral source (with each species having a species niche)
what is an example of a homologous structure?
pentadactyl limb in animal
(eg, mammals, birds, amphibians and reptiles)
what despite possessing similar bone arrangements animal limbs are dissimilar in terms of use, state 4 examples of their adaptive use
- human hand - tool for manipulation (power/precision of grip)
- bird and bat wings -flying
- horse hooves - for galloping
- what and dolphin fins- for swimming
what does continuous variation follow?
follow a normal distribution curve as the rate of change is gradual and cumulative
what will occur if 2 populations of a species are geographically separated with different ecological conditions? 2
- over time the 2 populations will adapt to the different environmental conditions
- gradually diverge from one another
what is the degree of divergence depend on when 2 populations are geographically separated? (3)
- extent of geographical separation and the amount of time since the separation occurred
- populations located in close proximity that separated recently will show less variation
- distance populations that separated a longer period of time ago will show more variation
what will happen to the degree of divergence between geologically separated populations the longer they are separated?
it will increase
what will occur as the degree of divergence increase the longer 2 populations are separated? (2)
- as the genetic divergence between the related populations increase, their genetic compatibility decreases
- eventually the 2 populations will diverge where they can no longer interbreed if returned to shared habitat
what occurs when 2 populations can no longer interbreed and produce viable, fertile offspring?
- they are separate species
what is the evolutionary process by which 2 related populations diverge in to separate species called?
speciation
what is an example of evolution?
peppered moths that exist in 2 distinct polymorphic forms (light colouration and darker melanic variant)
how does evolution of white and black peppered moths work?
- in an unpolluted environment the trees are covered by a pale-coloured lichen which provides camouflage
- in polluted environment sulphur dioxide kills the lichen, while soot blackens the break provides camouflage for the dark moth
what is the frequency of the 2 different forms of peppered moth dependent on? (4) with example
the environment
- before industrial revolution the environment was unpolluted and lighter moths had survival advantage
- after industrial revolution it was heavily polluted and there was a survival advantage for the darker moth
- recent environmental policies reducing pollution, altering the frequency of 2 population once again
