biodiversity and evolution

EVOLUTION

Evolution the relative change in

genetic traits of populations that

occurs over successive generations

microevolution gradual change in

allele frequencies in a population

over time

macroevolution large-scale

evolutionary changes including the

formation of new species or other

taxa

adaptation a structure, behaviour, or

physiological process that helps an

organism survive and reproduce in a

particular environment

Structural Adaptations

Behavioural Adaptations

Physiological Adaptations

Develop as a result of gradual change in the

genetic traits of members of a population

over time, and improve the chances of

survival and reproduction

Structural Adaptations are physical features on an

animal that have evolved over time to help them

survive and breed.

Camouflage

Eagle Claws

Eagle Vision

Burnt Cape cinquefoil - Hairy Leaves to retain

water

Behavioural Adaptations are changes in behavior that

certain organisms or species use to survive in a new

environment.

Migration

Hibernation

Dormancy

Physiological Adaptations refers to the

metabolic or physiologic adjustment within the cell,

or tissues, of an organism in response to an

environmental stimulus resulting in the improved

ability of that organism to cope with its changing

environment.

Harbour Seal - heart rate slows conserving oxygen

during dives

Temperature regulation in animals

Antifreeze in fish

VARIATION WITHIN A SPECIES

variation a visible or invisible

difference among some members of a

population

How does variation occur?

Sexual Reproduction is a source of variation. Through sexual

reproduction, parents pass down hereditary information

(genes) to their offspring.

The number of possible combinations of genes that offspring

can inherit from their parents results in great genetic

variation among individuals within a population.

Crossing Over Meiosis

Genetic variation is increased

by meiosis

Recombination or crossing

over occurs during prophase I.

Homologous chromosomes – 1

inherited from each parent – pair

along their lengths, gene by gene.

Breaks occur along the

chromosomes, and they rejoin,

trading some of their genes.

Mutations mutations are a source of

variation in populations. Mutations

happen continuously in the DNA of any

living organism. They can occur

spontaneously, when DNA is copied

before a cell divides.

A germ line mutation occurs in a sperm or

egg cell and the mutation may be passed

down to succeeding generations.

Thus, mutations are a significant source of

genetic variation in populations.

MUTATIONS CAN PROVIDE A SELECTIVE ADVANTAGE

Mutations that significantly alter proteins in

DNA often adversely affect the well-being of

an organism and can be harmful.

In some instances a mutation enables an

organism to survive in its environment

better, which, in turn, means that the

organism is more likely to survive and

reproduce.

This situation is more common when an

organism’s environment is changing.

Mutations that once were no advantage, or

perhaps were even a disadvantage, may

become favourable in a new environment. NATURAL SELECTION

Natural Selection is the process through which

populations of living organisms adapt and change.

Individuals in a population are naturally variable,

meaning that they are all different in some ways.

This variation means that some individuals have

traits better suited to the environment than

others.

Individuals with adaptive traits—traits that give

them some advantage—are more likely to survive

and reproduce.

These individuals then pass the adaptive traits on

to their offspring.

Over time, these advantageous traits become

more common in the population.

TYPES OF NATURAL SELECTION

stabilizing selection a form

of natural selection that

favours an intermediate

phenotype and acts against

extreme versions of the

phenotype.

directional selection a form of

natural selection that favours the

phenotype at one extreme over

the other

disruptive selection a form of

natural selection that favours the

extremes of a range of phenotypes

over intermediate phenotypes,

and may eliminate intermediate

phenotypes from the population

sexual selection a

special case of

natural selection in

which a particular

phenotype improves

an individual’s

chances of obtaining

a mate

INDUSTRIAL MELANISM

Industrial melanism is an evolutionary

effect prominent in several arthropods,

where dark pigmentation (melanism) has

evolved in an environment affected

by industrial pollution, including sulphur

dioxide gas and dark soot deposits.

The peppered moth has two colour

variations: greyish-white flecked with

black dots and black

Individuals of flecked and dark moth

populations fluctuated over relatively

short periods that corresponded to the

amount of air pollution in the moth’s

habitat.

ANTIBIOTIC RESISTANT BACTERIA

Some types of bacteria

not only pass down

their genes when they

reproduce, but also can

transfer their genes to

bacterial cells in their

own generation. This

form of gene transfer,

called horizontal

genetic transfer, is one

reason that genes for

antibiotic resistance

spread quickly in

bacterial populations. French naturalist Jean-Baptiste

Lamarck (1744–1829) outlined

his ideas about changes in

species over time. By comparing

current species of animals with

fossil forms, Lamarck observed

what he interpreted as a “line of

descent,” or progression, in

which a series of fossils (from

older to more recent) led to a

modern species. He thought that

species increased in complexity

over time, until they achieved a

level of perfection.

Lamarck also thought that characteristics, such as large muscles, that were

acquired during an organism’s lifetime could be passed on to its offspring.

Lamarck called this concept the inheritance of acquired characteristics.

inheritance of acquired characteristics idea that characteristics acquired during

an organism’s lifetime could be passed down to its offspring THIS IS NOT A

THING, YOU DO NOT GAIN SKILLS THAT YOUR PARENTS HAD OR THE TRAITS

THEY GAIN THROUGH USE.

if an adult giraffe stretched its neck to reach foliage high in the trees, then it

would pass down the trait for a long neck to its offspring

Lamarck provided a

hypothesis for how the

heredity of characteristics

from one generation to

the next might happen.

More importantly, he

noted that an organism’s

adaptations to the

environment resulted in

characteristics that could

be inherited by offspring.

DARWIN

In 1831, 22-year-old Charles Darwin left England on

the HMS Beagle, a British survey ship.

Charles Darwin was not the only person to organize

his and others’ observations and ideas into a

comprehensive theory to explain how species

changed over time.

Darwin called this process natural selection.

Darwin proposed two main ideas in On the Origin of

Species:

1. Present forms of life have arisen by descent and

modification from an ancestral species.

2. The mechanism for modification is natural

selection working for long periods of time.

Many of Darwin’s

observations surprised

him. For example, he

observed finch species

on the Galápagos

Islands that looked

similar and yet distinct

from one another and

from any finch species

on continental South

America. He

encountered marine

iguanas and giant

tortoises.. DARWIN'S OBSERVATIONS

1. The flora and fauna of the different regions the

Beagle visited were distinct from those Darwin had

studied in England and Europe. For example, the

rodents in South America were structurally similar

to one another but were quite different from the

rodents Darwin had observed on other continents.

If all organisms originated in their present forms

during a single event, Darwin wondered, why was

there a distinctive clustering of similar organisms

in different regions of the world?

Why were all types of organisms not randomly

distributed?

2. Darwin observed

fossils of extinct

animals, such as the

armadillo-like

glyptodont, that

looked very similar to

living animals.

Why would living and

fossilized organisms

that looked similar be

found within the

same region?

3. The finches and other animals Darwin saw on the Galápagos Islands closely

resembled animals he had observed on the west coast of South America.

Why did the Galápagos species so closely resemble organisms on the

adjacent South American coastline?

4. Galápagos species (such as tortoises

and finches) looked identical at first,

but actually varied slightly between

islands. Each type of Galápagos finch,

for example, was adapted to eating a

different type of food based on the

size and shape of its beak.

Why was there such a diversity of

species in such a small area?

Could these species have been

modified from an ancestral form that

arrived on the Galápagos Islands

shortly after the islands were formed?

5. Through his experience in

breeding pigeons and

studying breeds of dogs and

varieties of flowers, Darwin

knew that it was possible for

traits to be passed on from

parent to offspring, and that

sexual reproduction resulted

in many variations within a

species.

Could a process similar to

artificial selection also

operate in nature? FURTHER EVIDENCE OF EVOLUTION

fossil record remains or

traces of past life

preserved in sedimentary

rock, which reveal the

history of life on Earth

index fossils fossils that

are known to be common

during a particular time,

and so indicate the age of

the rock they are found in

1. Fossils found in young layers of rock

(from recent geological periods and

usually closer to the surface) are much

more similar to species alive today

than fossils found in deeper, older

layers of rock.

2. Fossils appear in chronological order

in the rock layers. So, probable

ancestors for a species are found in

older rocks, which usually lie beneath

the rock in which the later species is

found.

3. Not all organisms appear in the

fossil record at the same time.

The Ediacaran Period is a

geological period that spans

94 million years from the

end of the Cryogenian

Period 635 million years ago

(Mya), to the beginning of

the Cambrian Period 541

Mya.

The Ediacaran Period

produced some of the

earliest known evidence of

the evolution of

multicellular animals (the

metazoans).

The Cambrian Period was the first geological

period of the Paleozoic Era, and of the

Phanerozoic Eon. The Cambrian lasted 55.6

million years from the end of the Ediacaran

Period 541 million years ago (mya) to the

beginning of the Ordovician Period 485.4

mya.

The Cambrian Period marks

an important point in the history of life on

Earth; it is the time when most of

the major groups of animals first appear in

the fossil record. This event is sometimes

called the "Cambrian Explosion," because of

the relatively short time over which this

diversity of forms appears.

radiometric dating

method of dating

rocks and minerals

that uses

measurements of

certain radioactive

isotopes to

calculate absolute

age in years

transitional fossils fossils that show intermediary

links between groups of organisms

Transitional fossils link the past with the present.

For example, scientists have found fossilized

whales that lived 36 to 55 million years ago. These

fossils link present-day whales to terrestrial

ancestors. The Basilosaurus and Dorudon were

ancient whales that had tiny hind limbs, but led an

entirely aquatic life. Dorudon was about the size of

a large dolphin, about 5 m long. It had a tiny pelvis

(located near the end of its tail) and 10 cm legs,

both of which would have been useless to an

animal that lived an aquatic life. A more recently

discovered transitional form, Ambulocetus, had

heavier leg bones. Scientists hypothesize that it

lived both on land and in water.

Archaeopteryx show a

transitional stage in the

fossil record because this

species had

characteristics of both

reptiles (dinosaurs) and

birds. Archaeopteryx had

feathers, but, unlike any

modern bird, it also had

teeth, claws on its wings,

and a bony tail.COMPARATIVE ANATOMY

Comparative anatomy the comparative study of the body structures of

different species of animals in order to understand the adaptive changes they

have undergone in the course of evolution from common ancestors.

Despite their different functions, however, all vertebrate forelimbs contain the

same set of bones, organized in similar ways.

How is this possible?

The most

plausible

explanation is that

the basic

vertebrate

forelimb

originated with a

common ancestor.

homologous

structures

physical features

with the same

evolutionary

origin and

underlying

structural

elements, but

that may have

different

functions

analogous structures physical features

that evolved separately but perform

similar functions in different types of

organisms

Functional similarity in anatomy,

however, does not necessarily mean that

species are closely related.

The wings of insects, birds, bats, and

pterosaurs are similar in function, but not

in structure. (For example, bones support

bird wings, whereas a tough material

called chitin makes up insect wings.)

convergent

evolution

tendency among

species that are

not closely

related to

develop similar

body plans when

living under the

same conditions

vestigial structures anatomical features

that no longer retain their function

Some species have anatomical features

that appear to serve no function, such as

cave fish that have eye sockets but no

eyes. Vestigial structures are homologous

to functioning structures of other species.

Some large snakes and whales have

vestigial hip bones. Their small, unused

hip bones are homologous to the hip

bones that support the hind limbs of

other vertebrates. The evolutionary relationships

among species are reflected in

their DNA and proteins.

The field of molecular biology

developed as technologies to

identify molecules such as

DNA and proteins developed.

This field has provided

evidence that helps to

support the idea of common

ancestry and evolution

through natural selection.

The fact that all organisms use DNA as

their genetic material supports the

idea that all life has a common

ancestor.

Even seemingly unrelated species

share some of the same genes. The

chimpanzee (Pan troglodytes) and the

potato (Solanum tuberosum), for

example, have 2700 genes in common.

Scientists can infer how closely related

two species are by comparing

sequences in amino acids, RNA, and

DNA, or by comparing chromosomes

as a whole.

For example, human chromosome number 5 and its

chimpanzee counterpart show the same pattern of

bands, except for an inverted portion near the

centromere. Chimpanzees are our closest living

evolutionary relative.speciation the

formation of new

species

Transformation a

new species gradually

develops as a result

of mutation and

adaptation to

changing

environmental

conditions, and the

old species is

gradually replaced.

The evolution of mammoths followed this

pathway. The ancestral mammoth lived

approximately 2.6 million to 700 000 years ago. It

slowly evolved into the steppe mammoth that

lived 700 000 to 500 000 years ago, and finally into

the woolly mammoth that lived 350 000 to 10 000

years ago.

Divergence

(adaptative

radiation) one or

more species arise

from a parent

species that

continues to exist.

KEEPING POPULATIONS SEPARATE

geographical barrier feature such as

mountain that physically separates

populations and so prevents them

from interbreeding

Lava flow may isolate populations,

changes in ocean levels may turn a

peninsula into an island, or a few

colonizers may reach a geographically

separate habitat

After a long period of time, speciation

will occur. The separated populations

will no longer be able to mate and

reproduce successfully with other

members of the original population.

biological barrier features of

different populations that keep

them reproductively isolated, even

when they exist in the same

geographic area

Reproductively Isolated the

inability of a species to breed

successfully with related species

due to geographical, behavioral,

physiological, or genetic barriers or

differences.

Scientists studying the cichlids

hypothesize that many of the

species in the lake today

originated after the lake dried

to just a few small pools of

water about 14 000 years ago.

Populations were isolated in

these pools of water until the

water level rose again. The

speciation of cichlids has

produced a remarkable variety

of cichlids with a fascinating

diversity of teeth, jaws, mating

behaviours, and coloration.

prezygotic barrier a mechanism

that blocks reproduction from

taking place by preventing

fertilization.

Behavioural isolation

Ecological/habitat isolation

Temporal isolation

Mechanical Isolation

Gametic isolation

behavioural isolation biological barrier

in which species-specific signals or

behaviours prevent interbreeding with

closely related species

Male birds use distinct calls that are

recognized by other birds of the same

species during their mating season.

Their calls are different enough from the

calls of neighbouring species to provide a

biological barrier to reproduction.

Female spiders use pheromones

(chemical signals) to attract mates of the

same species.

Some male spiders use specific

movements to identify themselves to the

females.

Ecological/habitat isolation

biological barrier in which different

species live in the same general area,

but use different habitats, and so

rarely encounter each other

The blackspotted stickleback builds

nests in brackish waters, where

seawater and fresh water mix; the

three-spined stickleback builds nests

in fresh water. Habitat isolation is

different from a geographical barrier,

because there is no physical

impediment that keeps the

populations apart.

temporal isolation

timing barriers that

prevent species in the

same habitat from

interbreeding; species

may mate or flower at

different times of the

day, in different

seasons, or in different

years

mechanical isolation biological

barrier in which closely related

species have incompatible

reproductive structures, and so

either cannot mate, or, in the case

of plants, cannot be pollinated by

the same species of pollinator

Pollen may be carried on the backs

or wings of bees and flowers may

have different anatomy for

pollination.

Insects have very distinct locations

of their genital anatomy.

gametic isolation biological barrier,

such as a chemical marker on an egg,

that prevents eggs and sperm from

different species fusing to form a

zygote

Many marine animals, including corals,

clams, and sea cucumbers, release their

gametes into open water. The sperm

recognize eggs of their own species

through chemical markers on the

surface of the eggs. The sperm will not

recognize an egg of a different species,

and so will not fertilize this egg.

postzygotic barrier a

mechanism that blocks

reproduction after

fertilization and zygote

formation.

Hybrid inviability

Hybrid sterility

Hybrid breakdown

hybrid inviability a genetic

incompatibility of

interbred species that

stops development of the

hybrid zygote during its

development

hybrid embryos between

sheep and goats die in

early development before

birth.

hybrid sterility a biological

barrier that exists between

two species because,

although they can mate and

produce hybrid offspring, the

offspring are sterile

The offspring of a horse and

a donkey.

Meiosis fails to produce

normal gametes in hybrid

offspring.

hybrid breakdown a

biological barrier that

occurs when first

generation hybrids mate

with each other or with

an individual from either

parent species, and the

offspring are either sterile

or weak. population genetics the

study of genetic

variation in populations

gene pool sum of all

alleles for all the genes

in a population

genotype frequency

proportion of a population

with a particular genotype,

usually expressed as a decimal

phenotype frequency

proportion of a population

with a particular phenotype,

expressed as a decimal or

percent

allele frequency rate of

occurrence of a particular

allele in a population with

respect to a particular gene

genetic equilibrium

(Hardy-Weinberg

Equilibrium)

condition of a gene

pool in which allele

frequencies remain

constant over time,

and therefore the

population is not

evolving

FIVE CONDITIONS OF THE HARDY-WEINBERG

PRINCIPLE

1. The population is large enough that chance events will not alter allele

frequencies.

2. Mates are chosen on a random basis.

3. There are no net mutations.

4. There is no migration.

5. There is no natural selection against any of the phenotypes.

SOLVING HARDY-WEINBERG PROBLEMS

P2 + 2pq + q2 = 1

p + q = 1

P2 = frequency of homozygous dominant genotype (BB)

q2 = frequency of homozygous recessive genotype (bb)

2pq = frequency of heterozygous genotype

p = frequency of dominant allele

q = frequency of recessive allele

Sixteen percent of a population is unable to taste the chemical PTC. These

non-tasters are recessive for the tasting gene

1.)What percentage of the population are tasters?

The question is telling us q2 = 0.16 always change to decimal form.

The word population means P2, 2pq, or q2

If 16% are non-tasters then 84% have to be tasters

2.) What is the frequency of the dominant allele and

recessive allele?

The dominant allele is p so 0.6

The recessive allele is q so 0.4

3.) What percentage of the population are heterozygous for

the trait?

The question is asking for 2pq so you need to calculate it

2pq = 2(0.6)(0.4) = 0.48 = 48%

The delta-32 mutation, a recessive gene, gives humans protection from HIV

infection. The allele frequency for a town in Sweden is 20%.

Question is asking for q2 so q2 = 0.22 = 0.04 or 4% are immune to HIV

The question is telling us q = 0.2

1.) What percent of the population have two copies of the gene and are therefore

immune to HIV?

So p = 0.8

2.) What percent of the population are less susceptible to

HIV because they are heterozygous?

Question is asking about population so 2pq = 2(0.8)(0.2) = 0.32 or 32% CAUSES OF GENE POOL CHANGES

Mutations an

inheritable mutation

has the potential to

affect an entire gene

pool. Recall that while

most mutations are

neutral, some are

harmful and a few are

even beneficial.

gene flow net

movement of

alleles from one

population to

another due to the

migration of

individuals

non-random mating

mating among individuals

that prevents those with

particular phenotypes

from breeding, as in mate

selection or inbreeding

sexual selection a special case of natural

selection in which a particular phenotype

improves an individual’s chances of

obtaining a mate – a form of non-random

mating

Sexual selection generally involves

competition among males through combat

(as with rutting woodland caribou) or visual

displays to females. A male ruffed grouse

(Bonasa umbellus), for example, attempts

to attract females by displaying—fluffing up

his neck feathers and rapidly beating his

wings to produce a drumming sound.

Inbreeding occurs when closely related individuals breed

together. – also non-random mating

An extreme example of inbreeding is the self-fertilization

of some flowers.

Since close relatives share similar genotypes, inbreeding

increases the frequency of homozygous genotypes.

As homozygous genotypes become more common,

harmful recessive alleles are more likely to be expressed.

Inbreeding can also have a positive effect on a

population, however. If homozygous recessive

individuals fail to breed, and there are fewer

heterozygous individuals each generation, harmful

recessive alleles will be eliminated from the gene pool

over time

THE ROYAL FAMILY - HEMOPHILIA

The presence of hemophilia B within the European royal families was

well-known, with the condition once popularly known as "the royal

disease".

genetic drift change in allele

frequencies (gene pool) in a

small breeding population

due to chance events. stabilizing selection a form

of natural selection that

favours an intermediate

phenotype and acts

against extreme versions

of the phenotype.

directional selection

a form of natural

selection that favours

the phenotype at one

extreme over the

other

disruptive selection a form

of natural selection that

favours the extremes of a

range of phenotypes over

intermediate phenotypes,

and may eliminate

intermediate phenotypes

from the population