Achievement Standard 90717

Can You Describe Process and Patterns of evolution?

Learning Objectives

Processes of evolution◦ Describe ways in which speciation occurs (sympatric,

allopatric)◦ Describe reproductive isolating mechanisms that contribute

to speciation (geographical, temporal, ecological, behavioural, structural barriers, polyploidy)

◦ Explain the role of natural selection.

Patterns of evolution.Use the above process of evolution to explain/ discuss

◦ convergent evolution, ◦ divergent evolution (including adaptive radiation), ◦ co-evolution, ◦ punctuated equilibrium, ◦ gradualism.

Extra notes for the examIn the 2010 Exam… There will be an emphasis on groups that contain New Zealand

examples. However, the examination may also include contexts and examples from elsewhere in the world.

The significance of environmental changes, such as glacial/interglacial periods and associated changes in sea level, and their effects on speciation should be clearly understood.

Reproductive isolating mechanisms need to be considered in terms of how they contribute to speciation.

The concept of natural selection and its role in speciation should be clearly understood. Candidates should be able to recognise and describe: directional and stabilising selection.

For achievement with merit and achievement with excellence, candidates should be able to use the processes to explain and discuss the patterns.

Candidates should understand that evolutionary change at the level of species and populations reflects underlying changes in allele frequencies of the evolving populations.

ContentsNatural Selection.

◦Types of Natural Selection

Quotations on the species problem"... I was much struck how entirely vague and arbitrary is the distinction between species and varieties" Darwin 1859 (p. 48)[44]

"No term is more difficult to define than "species," and on no point are zoologists more divided than as to what should be understood by this word". Nicholson (1872) p. 20[45]

"The species problem is the long-standing failure of biologists to agree on how we should identify species and how we should define the word 'species'." Hey (2001)[40]

What determines a species?

The process of Speciation

Speciation is the evolutionary process by which new biological species arise

Two types – allopatric and sympatric speciation

Allopatric - emergence of a new species from populations that are geographically isolated.

Sympatric – not involving a period of geographical separation.

Natural Selection

Evolution (microevolution)- is where the allele frequency of a population changes over several generations.

Natural selection is one mechanism that can lead to evolution of a population.

Natural SelectionGenetic variation occurs among the individuals of any

population. Many of these differences do not affect survival (such as differences in eye colour in humans), but some differences may improve the chances of survival of a particular individual.

Eg: A rabbit that runs faster than others may be more likely to escape from predators,

Algae that are more efficient at extracting energy from sunlight will grow faster.

Individuals that have better odds for survival also have better odds for reproduction.

Natural Selection – “fittness”The concept of fitness is central to natural

selection. Individuals which are more "fit" have better potential for survival, ("survival of the fittest“). Modern evolutionary theory defines fitness not by how long an organism lives, but by how successful it is at reproducing. If an organism lives half as long as others of its species, but has twice as many offspring surviving to adulthood, its genes will become more common in the adult population of the next generation.