1. Evolution & Natural Selection (5.1-5.2)
IB Diploma Biology

2. Statement
Guidance
5.1.U1
Evolution occurs when heritable characteristics of species change
Workbook 137
5.1.U2
The fossil record provides evidence for evolution
Workbook 138
5.1.U3
Selective breeding of domesticated animals shows that artificial selection can cause evolution
5.1.U4
Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function
Workbook 140
5.1.U5
Populations of a species can gradually diverge into separate species by evolution
Workbook 141
5.1.U6
Continuous variations across the geographical range of related populations matches the concept of gradual divergence
Students should be clear that characteristics acquired during the lifetime of an individual are not heritable. The term Lamarckism is not required.
5.1.A1
Development of melanistic insects in polluted areas
Workbook 144
5.1.A2
Comparison of pentadacyl limb of mammals, birds, amphibians, and reptiles with different methods of locomotion
NOS
Looking for patterns, trends, and discrepancies – there are common features in the bone structure of vertebrate limbs despite their varied use

9. Pentadactyl Limbs Walk or crawl on land / Hind legs used for swimming
Organism (type)
Function of pentadactly limb
Crocodile (reptile)
Walk or crawl on land / Hind legs used for swimming
Penguin (bird)
Hind limbs for walking / forelimbs for swimming
Echidna (mammal)
All four limbs used for walking / Forelimbs for digging
Frog (amphibian)
All four limbs used for walking / Hindlimbs for jumping

10. Speciation

11. Evidence from Patterns of Geographical Variation

13. http://www. mr-sbiopage
Bonus on Test

14. Statement
Guidance
5.2.U1
Natural selection can only occur if there is variation among members of the same species.
Workbook 142
5.2.U2
Mutation, meiosis and sexual reproduction cause variation between individuals in a species.
Workbook 143
5.2.U3
Adaptations are characteristics that make an individual suited to its environment and way of life.
5.2.U4
Species tend to produce more offspring than the environment can support.
5.2.U5
Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring.
5.2.U6
Individuals that reproduce pass on characteristics to their offspring.
Students should be clear that characteristics acquired during the lifetime of an individual are not heritable. The term Lamarckism is not required.
5.2.U7
Natural selection increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics leading to changes within the species.
5.2.A1
Changes in beaks of finches on Daphne Major.
Workbook 145
5.2.A2
Evolution of antibiotic resistance in bacteria.
Workbook 146

15. Let’s Define Evolution
Biological evolution, simply put, is descent with modification.
small-scale evolution (changes in gene frequency in a population from one generation to the next)
large-scale evolution (the descent of different species from a common ancestor over many generations).
Evolution helps us to understand the history of life.

16. Pre-Read the article above
U5.1 - Natural selection can only occur if there is variation among members of the same species.
Pre-Read the article above

17. Critical Role of Variation
Variation is the only fundamental requirement for evolution to occur. (not Natural selection)
natural selection is a mechanism of evolution (one of several),
variation is a prerequisite for evolution.
There can be evolution without natural selection, but there cannot be evolution without variation.

18. Phenotype Influence P = G + E + (G*E)
The phenotype of an individual is influenced by several factors, and is represented in the following equation:
P = G + E + (G*E)
P = phenotype of individual
G = genotype of individual
E = environment of individual
G*E = interaction of genotype and environment
The phenotype of an individual is determined by the genotype of the individual (or the specific alleles and allele combinations it has inherited from its two parents), the environment that the individual was raised in, and an interaction between the individual’s genes and its environment.

19. Discrete Variability
Discretely varying traits are traits that can be put into categories,
Continuous Variability
Continuously varying traits cannot easily be put into categories.
best represented in a frequency distribution or histogram, since continuous traits vary along a continuum.

20. https://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_17

29. There are three main mechanisms by which genetic variation between individuals in a species may occur:
Mutations – Changing the genetic composition of gametes (germline mutation) leads to changed characteristics in offspring
Meiosis – Via either crossing over (prophase I) or independent assortment (metaphase I)
Sexual reproduction – The combination of genetic material from two distinct sources creates new gene combinations in offspring
Mutations
A gene mutation is a change in the nucleotide sequence of a section of DNA coding for a specific trait
New alleles are formed by mutation

30. Mutations - An organism's DNA affects how it looks, how it behaves, and its physiology — all aspects of its life. So a change in an organism's DNA can cause changes in all aspects of its life.
Mutations are random -mutations do not "try" to supply what the organism "needs." In this respect, mutations are random
Not all mutations matter to evolution
Since all cells in our body contain DNA, there are lots of places for mutations to occur; however, not all mutations matter for evolution.
Somatic mutations occur in non-reproductive cells and won't be passed onto offspring.
For example, the golden color on half of this Red Delicious apple was caused by a somatic mutation. The seeds of this apple do not carry the mutation.

31. There are three main mechanisms by which genetic variation between individuals in a species may occur:
Mutations – Changing the genetic composition of gametes (germline mutation) leads to changed characteristics in offspring
Meiosis – Via either crossing over (prophase I) or independent assortment (metaphase I)
Crossing Over
Crossing over involves the exchange of segments of DNA between homologous chromosomes during prophase I
The exchange of genetic material occurs between non-sister chromatids at points called chiasmata
As a consequence of this recombination, all four chromatids that comprise the bivalent will be genetically different
Chromatids that consist of a combination of DNA derived from both homologous chromosomes are called recombinants
Offspring with recombinant chromosomes will have unique gene combinations that are not present in either parent 

33. There are three main mechanisms by which genetic variation between individuals in a species may occur:
Meiosis – Via either crossing over (prophase I) or independent assortment (metaphase I)
When homologous chromosomes line up in metaphase I, their orientation towards the opposing poles is random
The orientation of each bivalent occurs independently, meaning different combinations of maternal / paternal chromosomes can be inherited when bivalents separate in anaphase I
The total number of combinations that can occur in gametes is 2n – where n = haploid number of chromosomes
Humans have 46 chromosomes (n = 23) and thus can produce 8,388,608 different gametes (223) by random orientation 
If crossing over also occurs, the number of different gamete combinations becomes immeasurable

34. There are three main mechanisms by which genetic variation between individuals in a species may occur:
Sexual reproduction – The combination of genetic material from two distinct sources creates new gene combinations in offspring
The fusion of two haploid gametes results in the formation of a diploid zygote  This zygote can then divide by mitosis and differentiate to form a developing embryo
As meiosis results in genetically distinct gametes, random fertilization by egg and sperm will always generate different zygotes
This means that individual offspring will typically show variation despite shared parentage

35. Adaptations are features of organisms that aid their survival by allowing them to be better suited to their environment
These adaptations may be classified in a number of different ways:
Structural: Physical differences in biological structure (e.g. neck length of a giraffe)
Behavioral: Differences in patterns of activity (e.g. opossums feigning death when threatened)
Physiological: Variations in detection and response by vital organs (e.g. homeothermy, colour perception)
Biochemical: Differences in molecular composition of cells and enzyme functions (e.g. blood groups, lactose tolerance)
Developmental: Variable changes that occur across the life span of an organism (e.g. patterns of ageing / senescence)

36. Biological adaptations have a genetic basis (i. e
Biological adaptations have a genetic basis (i.e. encoded by genes) and may be passed to offspring when the parents reproduce
Organisms with beneficial adaptations will be more likely to survive long enough to reproduce and pass on these genes
Organisms without these beneficial adaptations will be less likely to survive long enough to reproduce and pass on their genes
Hence adaptations result in differential reproduction within a species, allowing for natural selection to occur

37. Over reproduction
The Malthusian dilemma was proposed by English clergyman Thomas Malthus who identified that populations multiply geometrically (i.e. exponential progression), while food resources only increase arithmetically (i.e. linear progression)
In other words, species tend to produce more offspring than the environment can sustainably support
If left to follow course, a stable population will inevitably outgrow its resource base, leading to competition for survival
When there is an abundance of resources,  a population will grow according to its biotic potential (exponential J-curve)
With more offspring, there are less resources available to other members of the population (environmental resistance)
This will lead to a struggle for survival and an increase in the mortality rate (causing population growth to slow and plateau)
This concept is central to Darwin’s understanding of ‘survival of the fittest’ – any trait that is beneficial for competitive survival will be more likely to be passed on to offspring according to natural selection

48. The Finches of Daphne Major

49. Adaptive radiation describes the rapid evolutionary diversification of a single ancestral line
It occurs when members of a single species occupy a variety of distinct niches with different
environmental conditions
Consequently, members evolve
different morphological features
(adaptations) in response to the different
selection pressures
An example of adaptive radiation can
be seen in the variety of beak types seen in the finches of the Galapagos Islands
These finches have specialized beak shapes depending on their primary source of nutrition (e.g. seeds, insects, nuts, nectar)

56. for writing a 1 page reflection
Bonus
for writing a 1 page reflection
Watch the Netflix documentary
“Resistance”

57. Practice
Label each box (numbered 1-5) in the RULE column on the page called “Summary of Evolution by Natural Selection” with the following words:
1:  Overproduction
2:  Variation
3:  Selective Pressure
4:  Differential Survival and Reproduction
5:  Population change

58. Bibliography / Acknowledgments
Jason de Nys
Chris Paine