Presentation on theme: "Level 3 Biology Patterns of Evolution. Things to learn (in brief) Patterns of evolution. Use the process of evolution: speciation (sympatric, allopatric)"— Presentation transcript:
Things to learn (in brief) Patterns of evolution. Use the process of evolution: speciation (sympatric, allopatric) reproductive isolating mechanisms (geographical, temporal, ecological, behavioural, structural barriers, polyploidy) and natural selection. to explain/ discuss convergent evolution, divergent evolution (including adaptive radiation), co-evolution, punctuated equilibrium, gradualism.
Patterns – summary Patterns repeat – so a pattern in evolution is simply common themes in the way species change. Patterns of evolution include Sequential Divergent Convergent Coevolution Gradualism Punctuated equilibrium These are all labels that we give to different common themes in the natural world. But nature is round not square – so in most situations we will see a mixture of these patterns together. See evolution of mammals
Convergent evolution In evolutionary biology, convergent evolution is the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. It is the opposite of divergent evolution
Divergent evolution In evolutionary biology, convergent evolution is the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. It is the opposite of divergent evolution
COEVOLUTION The rough-skinned newt… produces a toxin to deter predation from the garter snake. The garter snake has developed resistance to this toxin, leading the newt to produce an ever more toxic poison. The poison in a newt is enough to kill 30 people.
COEVOLUTION The bullhorn acacia thorns and Beltian bodies at leaflet tips provide food for a species of ant. The ants, in turn, live in the hollowed out area and vigorously protect the acacia from other insects and browsing animals. Predators often coevolve with their prey – developing increased agility, and hunting techniques, while the prey evolves defence strategies and camouflage. Lab manual page 263/4 “Arms Race” – Animal Battle at Kruger National Park
RATE OF EVOLUTION At times researchers have found that species change very little over long periods of time, then change rapidly, or disappear suddenly. At other times species have been found to gradually change. Gradualism Punctuated Equilibrium Which of these occurs seems to depend on the species and the events at the time. Lab manual page 258
HOMOLOGOUS STRUCTURES Relationships between species is often assessed by looking at shared physical features, called homologous structures. Ancestors have this feature and pass it on to their descendants, but as they evolve to different niches, the feature may be used in different ways. A classic example is the pentadactyl limb passed on to all land living vertebrates by their amphibian ancestor.
MAMMAL EVOLUTION Mammals have been around for quite a while. However, in the late Cretaceous something happened to the dinosaurs, a host of new niches became available, and the mammals quickly took advantage of them. Lab manual page 265/6/7 I am here!
RATITE EVOLUTION It is a thought that all modern birds evolved from Archaeopteryx. The Ratite group split off much earlier than other birds, then as they were isolated by continental drift, Allopatric speciation occurred. Lab manual page 269-70
NZ PARROT EVOLUTION NZ’s parrots give a great local example of evolution. An Australian ancestor came here about 100mya. Of course at that stage there wasn’t far to go… Differing selection pressures… differing niches… no gene flow… The kaka and kakapo inhabited the forest, and later, as mountain building occurred, the kea evolved. Lab manual page 277/8
OTHER WORK… Other bits worth looking at… time dependent. Extinction (pg 272) Land snails (275/6) Hebe (281) Ancient NZ landscape (273) Wrens (279-80) NZ Invertebrates (274)
HUMAN STUFF - INBREEDING Pitcairn Island: Mutiny on the Bounty (1789): Population of 9 mutineers, 8-9 Tahitian females and 6 Tahitian males to uninhabited Pitcairn Island. Mennonites: Religious isolate; suffer from MSUD (autosomal recessive on c'19) at high rates. Inability to metabolize 3 amino acids, 20% die. Afrikaners, South Africa: Fanconi anemia (autosomal recessive on c'16); red-cell defects. Azores: Atlantic Islands; High incidence of Machado-Joseph disease (autosomal dominant on c'14). Late onset motor ataxia. Yemeni Jews : PKU (amino acid processing disease) high among them (religious isolate). Tristan da Cunha Island, Atlantic: Retinitis Pigmentosa (eye disorder).