Unit 4: evolution

Vocabulary

1. Evolution: Descent with modification; changes in the gene pool of a population over time; the idea

that living species are descendants of ancestral species that were different from the present-day ones;

also defined more narrowly as the change in the genetic composition of a population from generation to

generation.

Divergent Evolution: the process whereby organisms that have different adaptations from their

recent ancestors survive in changed habitats; or, the process whereby organisms with a recent

common ancestor develop different adaptations in different habitats. (Ex. Darker coloured

moths survived a highly polluted area where the trees darkened while white moths died out).

Convergent Evolution: Species evolve from different origins but under similar environmental

conditions to have similar traits. (ex. Aardvarks and anteaters)

Adaptive Radiation: when a single ancestral species evolves into a number of different species.

Co-evolution: process by which species that are tightly linked with one another (ie. flower and

pollinator) evolve gradually together.

*The following are different pieces of evidence that support the theory of evolution:

Palaeontology: the study of fossils; through fossils, many similarities of extinct organisms have

been found in relation to modern day organisms.

Biogeography: the study of the distribution of plants and animals in the environment; similar

animals show up in different places all over the world, in places where they’d never come in

contact with each other. Evolution from a common ancestor would lead to these similar

characteristics, as they would evolutionize differently in different environments.

Heredity: similarities have been found in the genetic sequences of seemingly unrelated animals,

suggesting a common ancestor.

Embryology: the study of the development of an organism; many embryos in early development

are almost identical to very different species.

Comparative Anatomy: the study of the anatomy of various animals; many animals have

similarities in structures and functions of their anatomy:

o Homologous Structures: features of animals that are structurally similar but functionally

different. (ex. a whales fin to a birds wing to a human arm)

o Analogous Structures: features of animals that are functionally similar but structurally

different. (ex. the eyes of scallops, insects and humans).

2. Molecular Biology: The branch of biology that deals with the structure and function of the

macromolecules (e.g., proteins and nucleic acids) essential to life; similarities can be found between

species in their genomes.

3. Variation: differences in characteristics of a species due to genetics; some may be insignificant, while

others may affect the survival of the individual.

4. Industrial Melanism: prevalence of dark-colored

varieties of animals (esp. moths) in industrial areas

where they are better camouflaged against

predators than paler individuals. The best example

of this is the peppered moth in England during the

industrial revolution. Before the revolution, trees

were light in color, giving light colored moths an

advantage. However, after the revolution, dark

colored moths were at an advantage, and today,

dark moths are more common than light ones in

England. This is important for three reasons:

Shows that evolution is an interaction between the organisms and the environment.

Shows the presence of variation within the population.

Shows that evolution can act on genetic variability.

5. Catastrophism: the idea proposed by fossil hunter George Cuvier that states that catastrophes (ie.

Floods, eruptions) had periodically destroyed species in one area while not affecting species in a nearby

area. He drew this conclusion from the observation that new species appeared as others disappeared

from the fossil record.

6. Jean Baptiste Lamarck: theologian (person who studies and makes theories) who proposed laws of

evolution that were later proved to be incorrect.

Law of Use or Disuse: “If an organism uses a particular organ, it will remain active and strong. If

an organism does not use a particular organ, it will eventually disappear.” This law was not

accepted as it suggested that a single organism could just changes its own structure to suit its

needs, which is not possible.

Law of Inheritance of Acquired Characteristics: “The characteristics of an organism developed

through the use and could be passed on to the offspring of the generation.” This law was not

accepted because acquired characteristics cannot be inherited; only genetics can.

o NOTE: All experiments conducted to support these theories failed, further disproving them.

7. Hardy-Weinberg Law of Equilibrium: this law states that a population will be in genetic equilibrium if

it meets five specific conditions: (1)Large population; (2)No mutations; (3)No In of Out [no immigration or emigration]; (4)No sexual selection [random mating]; (5)No natural selection.

In other words, the theory is impossible, although it does have some functions. There are two formulas

with the Hardy-Weinberg theories (where p and q represent opposite alleles or genotypes):

Allele Frequency Formula (p + q = 1): using this formula, you can find the frequency of one allele

once give the other. (Ex. if allele R is 0.7, then allele r must be 0.3 because 0.7 + 0.3 = 1)

Genotype Frequency Formula (p2 + 2pq + q2 = 1): in this equation, p2 represents the

homozygous dominants, 2pq represents the heterozygous, and q2 represents the homozygous

recessive. You can pair this formula with the first to answer questions about allele frequencies.

o Example 1: 16% of a fruit fly population as green eyes (recessive trait). What is the allele

frequency for red eyed flies?

Because q2 is used for homozygous recessive, we say:

q2 = 0.16

q = 0.4 (Allele frequency for green eyes)

We now plug this in to find the other allele frequency.

q + p = 1

0.4 + p = 1

p = 1 – 0.4

p = 0.6

o Example 2: 9% of the fruit flies have green eyes (recessive trait), 49% are homozygous

for red eyes. How many are heterozygous (%)?

We first find p and q, then plug that into 2pq (which represents the

heterozygous).

p2 = 0.09 q2 = 0.49

p = 0.3 q = 0.7

Plug it in: 2pq = % of heterozygous [2 x 0.3 x 0.7] = 42%

Note: the

percentages all

add up to 100%!

8. Charles Darwin: a theologian that traveled the world on the HMS Beagle

studying evolution, particularly the finches of the Galapagos Islands. The

only weakness in Darwin’s theories was that they did not account for how

these changes happen (genetics). As that was later proven by Mendel, it

became an accepted theory.

Malthus’ Essay: an essay on the principles of human population

that helped with Darwin’s conclusions. It stated that the ever

increasing human population was exceeding the food supply

needed to feed it; to keep a balance between the need to food and

the supply for food, millions of individuals died by disease,

starvation or war. Darwin realized that this competition is true of

all organisms.

Selective Breeding: the selection of who breeds with who, whether in nature or with human

interference; Darwin realized that this could affect a population over time.

Charles Lyell: a geologist that proposed that the earth was very old and ever changing. This

theory is known as uniformitarianism. This idea led Darwin to think that organisms was be

changing in the same way.

Observations: Darwin noted many things, such as larger beaks for birds that ate larger nuts. His

theories are accepted today as the correct facts of evolution. This led him to believe that these

animals adapted to their needs.

*Below are Darwin’s Final Conclusions.

Overproduction: most species produce more offspring than are needed because many of them

will likely die.

Competition: all organisms compete for food and living space.

Variation: Individuals of species have their own minor differences from one another, and these

variations may affect the individual’s chances of survival.

Adaptations: because of variations, traits that are more likely to help an individual survive will

be passed on to offspring, adapting the species over time.

Natural Selection: “survival of the fittest;” individuals with the best advantages to survival will

reproduce.

Speciation: over time, adaptations will make an organism so different from what it was that it

will be designated a new species.

9. Alfred Wallace: another theologian that came to many of the same conclusions as Darwin around the

same time period.

10. Lamarck vs. Darwin: Darwin’s theory won over Lamarck’s, however their theories did have some

similarities as well as differences.

Similarity: both believed that evolution was related to the environment.

Differences: Lamarck believed that individuals evolved, while Darwin believed that species

evolved as solid populations. Also, Lamarck believed that an individual would decide on the

change after an event, whereas Darwin believed that we were ever changing with variation as

the environment was ever changing.

11. Relative Dating: because most fossils are formed in sedimentary rock, we can

determine the relative age of a fossil by examining the rock in which it was found.

Generally, those found deeper are older, and those found higher are younger.

12. Radioactive Dating: the most accurate way to age fossil and rock; it is based off of the radioactive

decay of isotopes that an organism accumulated in their lifetime; the rate of this break down is called

half-life (the amount of time it requires to breakdown half of the originally accumulated isotopes and

having it replaced by one half decay product).

The easiest way I’ve found to find the age of a rock is by using the following formula:

Age = tknown half-life × log10(current amount ÷ original amount) ÷ log10(1/2)

EXAMPLE 1:

The half life of uranium-238 is about 4.5 billion years. A rock containing uranium is found with only ½

of the original amount of uranium-238. The age of this rock in billions of years is approximately what?

Age = tknown half-life × log10(current amount ÷ original amount) ÷ log10(1/2)

Age = 4.5 × log(0.5 ÷ 1) ÷ log(0.5)

Age = 4.5 × log(0.5) ÷ log(0.5)

Age = 4.5

4.5 billion years old

EXAMPLE 2:

If the half life of radioactive carbon (C14) is 5730 years, what is the age of a bone with 4% C14 (a

modern bone has 16%)?

Age = tknown half-life × log10(current amount ÷ original amount) ÷ log10(1/2)

Age = 5730 × log10(0.04 ÷ 0.16) ÷ log10(0.5)

Age = 5730 × log10(0.25) ÷ log10(0.5)

Age = 11460

11460 years old

13. Biodiversity: the variety of life in the world or in a particular habitat or ecosystem. Biodiversity is

supported by 5 main factors:

Mutations: a mutation will alter gametes that are handed down to later generations.

Genetic Drift: in small populations, frequencies can be severely altered by chance (ie. more red

bugs just happen to get eaten then green bugs). Because the population is so small, this could

have a strong effect on the gene pool, leading to more biodiversity.

o Bottleneck Effect: when chance greatly reduces a population (ie. natural disaster,

overhunting, habitat destruction). This leaves certain alleles in the gene pool – some

other alleles may have disappeared entirely.

o The Founder Effect: when a small number of individuals colonize a new area who do not

carry all of the traits of the original parent population (ex. all of the red haired

individuals decide to colonize a new area – therefore, nobody in the new colony will

ever have brown hair, even if their parents did).

Original Population Bottleneck Effect Surviving Reproduction of

Population Survivors

Gene Flow: the movement of alleles in and out of a population via emigration and immigration.

This may lead to two slightly different populations slowly having less and less differences from

one another.

Non-Random Mating (Sexual Selection): individuals tend to mate with individuals that they feel

will give their offspring the best chance of survival.

Natural Selection: A process in which individuals that have certain inherited traits tend to

survive and reproduce at higher rates than other individuals because of those traits.

o Stabilizing Selection: a type of natural

selection in which genetic diversity decreases

as the population stabilizes on a particular

trait value; Mode of natural selection by

which intermediate phenotypes in the range

of variation are favoured and extremes at

both ends are eliminated.

o Directional Selection: directional selection

occurs when natural selection favours a single

phenotype and therefore allele frequency

continuously shifts in one direction. (ex.

brown beetles living in mud will outlive green

beetles living in mud).

o Disruptive Selection: describes changes in

population genetics in which extreme values

for a trait are favoured over intermediate

values.

14. Speciation: the formation of a new species through adaptation.

Adaptation: any trait that enhances an organism’s ability to survive that is passed down through

generations.

Biological Species: a group of organisms that can interbreed and produce fertile offspring and

who breed at the same times of the year.

o Hybrid Species: an organism that successfully

develops from two different species but who is

sterile (ex. donkeys and horses can make mules)

Transformation: when one whole species evolves into

another.

Divergence: when two or more species arise from one

parent species

o Allopatric Speciation: divergence whereby the

species is separated by a physical barrier (Ie. Mountains, island, etc.) and evolve

individually.

o Sympatric Speciation: when individuals within

the population can no longer successfully breed

with one another, the two fertile groups

separate.

Prezygotic Barriers: when fertilization

cannot occur between two individuals.

Behavioural Isolation: when

the reproductive behaviour (ie.

a mating dance) differs from

another to the point that they

will not mate.

Habitat Isolation: when two

species live in different habitats or niches.

Temporal Isolation: when mating times of the year differ from that of

other species, and will therefore not mate.

Mechanical Isolation: anatomy makes fertilization impossible (ex. a

Chihuahua and a Great Dane)

Gamete Isolation: when gametes are chemically unable to fuse.

Postzygotic Barriers: when a fertilized egg cannot produce a successful and

fertile organism.

Hybrid In-Viability: zygote never fully develops because of incompatible

genes.

Hybrid Sterility: organism is produced but is sterile (ie. donkey and a

horse make a mule)

Hybrid Breakdown: if the first generation is successful but the second

or third is weak and dies.

15. Gradualism: the belief that species arise through gradual

changes accumulated over time (Darwin); the opposite of

punctuated equilibrium.

16. Punctuated Equilibrium: the belief that species remain

constant for long periods of time and then arise into new

species in a short period of time, interrupting the original

equilibrium and bringing about a new equilibrium (Gould

and Eldridge); the opposite of gradualism.

17. The Origin of Life: there are many theories of where life began.

Panspermia Theory: theory that life on earth originated from a migrating species from outer

space, either brought here by accident or by an intelligent being.

Intelligent Design: the concept that all biological origins on earth have followed a pattern which

set out as a product of some intelligent cause, concluding that life is too complex to be by

chance.

Gaia Hypothesis: the suggestion that Earth is one huge, living, self-regulating system; proposed

by James Lovelock.

Lynn Margulies Hypothesis (Symbiogenesis): the theory that mitochondria and chloroplasts

(major organelles in cells) used to be single-celled prokaryotes and later fused into cells, creating

a symbiotic relationship.

Haldane-Oparin Hypothesis (Heterotrophic Hypothesis): the widely accepted theory that

suggests that the first organic compounds were formed by natural chemical processes on the

primitive earth and that the first life like structures developed from large heterotrophic protein

molecules that resulted from those reactions. They suggest that the world had to of been very

hot and consisting only of Hydrogen, Water, Ammonia, and Methane; the oceans were near

boiling temperature; energy from UV ray, lightening and volcanoes would be enough to begin

the necessary reactions to make the first cell like

structures. This theory works with the theory of

Symbiogenesis as well. Once these reactions began

to take place, oxygen became a by-product (as

cells learned to photosynthesize), which eventually

led to the world we know today.

o Miller and Urey: conducted an experiment

that proved that the Haldane-Oparin

Hypothesis was physically possible. They

took the assumed materials of the

primitive Earth (water, hydrogen, methane

and ammonia), placed them in a flask, and

exposed the mixture to sparks (to mimic

lightening). The flask then produced tiny

organic compounds that could build a cell.