Natural Selection, Evolution & Taxonomy IB Biology Review Natural Selection, Evolution & Taxonomy

Vocabulary Homologous structures The arms, forelegs, and flippers of different mammals represent variations on a basic structural theme that have changed through natural selection to adapt to specific environments Vestigial Structures Certain anatomical structures no longer have a use, but presumably, they had a use in the distant ancestor of the species; ex: blind cave salamanders, and the vestigial “legs” of whales Mimicry occurs when a group of organisms, the mimics, have evolved to share common perceived characteristics with another group, the models (i.e. a nonpoisonous organism copying the markings of a poisonous one)

Definitions Natural Selection Evolution Greater survival and reproductive success of individuals with favorable heritable variations can lead to change in the characteristics of a population Evolution Evolution is the cumulative change in the heritable characteristics of a population

Darwin’s Theory of Natural Selection

What causes natural selection to occur? Mutations in DNA caused by replication mutations over- or under-expression of genes environmental factors Differences allow one individual to have an advantage over another

Stabilizing Selection Curves

How does natural selection lead to evolution? Variation within the species is necessary (caused by genetic mutations and meiosis) This variation is important because there have to be differences (sometimes undetectable or at the cellular level) which give one member of a species a slight advantage over its fellow species member There also must be overproduction (overpopulation) and a struggle for existence This is important because the variation between individuals would be unimportant and would not lead to individual “advantages” if there were enough “resources” to go around. Ie. There have to be “winners and losers” in evolution. Some members (the “winners” of the species) with the desirable trait(s) survive and reproduce at a higher rate. Over years and years, the phenotypic traits (and their underlying genes) that led to their success will become more common in the “gene pool

Two Theories of Evolution Punctuated Equilibrium evolution occurs in relation to environmental changes; new traits are put to the test when the environment changes abruptly Gradual Evolution evolution that occurs slowly over time, with organisms evolving towards a “natural perfection”

Evidence of Evolution Fossil Records The fossil record indicates that living organisms have progressed from simple to more complex over time Selective Breeding of Domesticated Animals through artificial “selection,” people have been changing species such as pigs, cows, dogs etc. to suit our needs and desires for millennia Homologous Structures represent variations on a basic structural theme that have changed through natural selection to adapt to specific environments i.e. common cilia structure in paramecium and human windpipes

Taxonomic Classification What is the order of the categories? Kingdom Phylum Class Order Family Genus Species

Taxonomic Classification What pneumonic can be used to remember the order? Kingdom Phylum Class Order Family Genus Species King Phillip Can Operate For Good Spines

Multiple Choice-1 Classification in biology involves putting organisms that share characteristics together in groups. In which type of group do the organisms share the most characteristics? A. Class B. Family C. Genus D. Order Correct answer: C

Multiple Choice-2 What statement can be made about members of the same order? A. They all belong to the same genus. B. They all belong to the same class. C. They all belong to the same family. D They can all interbreed successfully. Correct answer: B

Which names are usually used to identify an organism? Genus, species Example: humans Genus: homo Species: sapiens

Multiple Choice-3 Correct answer: C The scientific names of two organisms are shown below. Quercus alba Angelica alba What is the relationship between these organisms? A. They both belong to the same genus but they are different species B. They both belong to the same species but different genera C. They are both different species and different genera D. They both belong to the same species and the same genus Correct answer: C

Multiple Choice-4 Which statement most accurately describes the plants Clarkia cylindrica, Clarkia deflexa, and Clarkia similis? A. All three belong to the same species. B. Each belongs to a different group. C. All three belong to the same family. D. Each belongs to a different family. Correct answer: C

5 Basic Kingdoms of Living Things Basic information about all five kingdoms At the kingdom level, these above characteristics are used to separate living groups, but at lower taxonomic levels (phyla, class, order, family, genus) some of the characteristics used to separate groups are: Morphology What they look like Reproduction How they reproduce Energy/Food How they obtain or process it Genetic similarities/differences****

How Classification Works What are the three usual characteristics used? Morphology What they look like Reproduction How they reproduce Energy/Food How they obtain or process it What is the best method? Genetics This is the most reliable method

What IB Wants You will need to be able to: List seven levels in the hierarchy of taxa—kingdom, phylum, class, order, family, genus and species—using an example from two different kingdoms for each level. Distinguish between the following phyla of plants, using simple external recognition features: bryophyta, filicinophyta, coniferophyta and angiospermophyta. Distinguish between the following phyla of animals, using simple external recognition features: porifera, cnidaria, platyhelminthes, annelida, mollusca and arthropoda. Apply and design a key for a group of up to eight organisms.

IB Exam Question 1. Explain evolution of a species by natural selection in response to environmental change. (7 marks) species show variation; variation is inherited; species have the potential to produce more offspring than can survive; this leads to a struggle for existence / survival; resources are limited; those that are best adapted (on average) survive to reproduce; this leads to a population adapted to the environment; as the environment changes those that are best adapted will leave more offspring; this will cause the species to evolve to a new adaptation / change in gene frequencies;

IB Exam Question 2. Explain two examples of evolution in response to environmental change; one must be antibiotic resistance in bacteria (8-10 marks) The Galapagos Islands are near each other, but each has a unique environment (this is the environmental change/difference) A common ancestor of all current Galapagos finches came from the S. American mainland (these islands are off the coast of S. America) The food available on the islands was: seeds (various sizes), flowers, insects, and plant buds. There was/is a struggle for existence among the finches (for food ). Only those finches with beaks adapted to the available food survive and reproduce – thereby transmitting their genes to the next generation. Each finch species adapted over thousands of years to certain niches in their food gathering capabilities. Their beak shape was very important and therefore changed to suit the food source.

IB Exam Question 2. Explain two examples of evolution in response to environmental change; one must be antibiotic resistance in bacteria cont. (8-10 marks) environmental changes (e.g. application of antibiotics); affects some individuals more than others; individuals with antibiotic resistance mutation survive; to reach reproductive age / breed to pass on alleles; result is resistance is best adapted allele / become more frequent in population; this is referred to as natural selection; results in change in species with time / change in allele frequency; this is termed evolution; discussion of punctuated equilibrium / gradualism;