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

2. 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)

3. 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

4. Darwin’s Theory of Natural Selection

5. 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

6. Stabilizing Selection Curves

7. 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

8. 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”

9. 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

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

11. 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

12. 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

13. 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

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

15. 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

16. 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

17. 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****

18. 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

19. 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.

20. 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;

21. 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.

22. 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;