Presentation by Abdul Qadeer MBBS; DTM; BASc; CPHI-C, CIC

St. Clair College Continuing Education

ESSENTIALS

OF HUMAN

ANATOMY &

PHYSIOLOGY

Evolution

Evolution – Non Technical

Evolution is the accumulation of changes

through succeeding generations of organisms

that results in the emergence of new species

Since the origin of life , evolution has

transformed the first species (the common

ancestor of all living things) into a large

number of different species

Evolution – In Biology

Evolution is the change in the inherited traits

of a population from one generation to the

next

These traits are the expression of genes that

are copied and passed on to offspring during

reproduction

Mutations in these genes can produce new or

altered traits, resulting in heritable differances

between organisms

Evolution – In Biology

New traits can also come from transfer of

genes between populations, as in migration,

or between species, in horizontal gene

transfer

Evolution occurs when these heritable

differences become more common or rare in a

population, either non-randomly through

natural selection or randomly through

genetic drift

Evolution

Earth was created on

Sunday

October 23, 4004 BC

Archbishop James

Ussherof Armagh

(1581-1656)

Evolutionary Theories

Evolutionary Theories

The acceptance of theories of evolution has

never been universal

Many people hold cultural and religious

beliefs about the origin of life

May not be in harmony with scientifically

accepted reasoning and conclusions

Evolutionary Theories

A Irish scholar and

theologian published his

calculations for the age

of Earth based on

astronomy, history, and

biblical sources.

Declared that Earth was

created on Sunday,

October 23, 4004 BC. Archbishop James

Ussherof Armagh

(1581-1656)

Evolutionary Theories

Also calculate the dates of other significant

biblical events.

In 1701, his chronology was printed as

marginal notes in an authorized version of the

Bible.

About 150 years later, most Europeans

mistakenly thought his chronology was part

of the original scripture.

Evolutionary Theories

Today

Most people understand that the world is a

dynamic environment in which change is

both natural and unavoidable

Evolution

The process in which significant changes

in the inheritable traits (i.e. the genetic

makeup) of a species occur over time

Evolutionary Theory

500 years ago

Most people thought that their natural

surroundings changed very little

Immutable

Unchanged and unchanging, believed

(before evolutionary theory became

accepted) to be characteristic of life forms

Evidence From the Past

Fossil Record

Strong evidence for a changing Earth

began with a careful examination of

fossils.

Near the end of the 15th century, the

scientist were convinced that Earth's

surface had changed dramatically over

time.

Fossils offer evidence of environmental

change

Fossil Record

Fossils

Any preserved remains or traces of an

organism or its activity; many fossils are

of such hardened body parts as bone

Fossils

(a) Reconstructed

mammoth skeleton

(b) skull of a

young male

Homo erectus

(c) Pterodactylus

kochi from the

Jurassic period

Fossils

Permineralized fossil

A fossil formed when dissolved minerals

precipitate from a solution in the space

occupied by the organism's remains

Permineralized fossil

(a) dead organism

(b) organism is buried and compressed under many layers of sediment

Permineralized fossil

(c) under high pressure deposits harden to form sedimentary rock and the fossil remains become mineralized

(d) erosion or excavation of sedimentary rock exposes fossil remains on the surface

Fossilization

Fossilization

The process by which traces of past

organisms become part of sedimentary

rock layers or, more rarely, hardened tar

pits, volcanic ash, peat bogs, or amber

Microfossils

Microscopic remains of tiny organisms or

structures that have hard and resistant

outer coverings

Fossilization

Insect fossilized in amber

Study of Fossils

Palaeontology

The scientific study of fossil remains

Catastrophism Theory

Baron Georges Cuvier (anatomist) in 18th centaury

Did not believe that species changed overtime

Numerous global catastrophes in the past had repeatedly caused the extinction of species that were then replaced by newly created forms

Catastrophism

Discrete rock layers

containing different

fossils reinforced the

idea that the Earth's

history could be divided

into ages marked by

catastrophic change

However, gradual

change, like that caused

by erosion, has also

played an important role

in the Earth's history

Fossil Record

Cuvier’s hypothesis

Relative age

An estimate of the age of a rock or fossil

specimen in relation to another specimen

Absolute age

An estimate of the actual age of a rock or

fossil specimen

Scientist of that time had no precise

method for calculating absolute age

Absolute Age of Earth

Estimate 4.6 billion years

Radioactive decay

The release of subatomic particles from

the nucleus of an atom, which results in

the change of a radioactive parent isotope

into a daughter isotope; when a number of

proton is altered, a new element is formed

Absolute Age of Earth

Radioisotopes

Atoms with an unstable nuclear

arrangement that undergo radioactive

decay

Parent isotopes

Daughter isotopes

Provide an accurate and reliable method of

determining the age of both rock and

fossil remains

Early Ideas About Evolution

Actualism Theory

James Hutton (1795- 1830)

The same geological processes occurring

in the present also occurred in the past

Uniformitarianism Theory

Sir Charles Lyell (1797-1875)

The Earth's surface has always changed

and continues to change through similar,

uniform, and very gradual processes

Early Ideas About Evolution

Lyell found evidence that valleys were formed

through the slow process of erosion, not by

catastrophic floods.

Early Ideas About Evolution

The ideas of Hutton and Lyell led to an

understanding of "the rock cycle" as we know

it today

Early Ideas About Evolution

Spontaneous Generation Theory Chevalier de Lamarck (1744-1829)

Living organisms arise from nonliving matter

Acquired Traits Theory

Chevalier de Lamarck (1744-1829)

First scientist to recognize that the environment

plays a key role in the evolution of species

Changes in an individual resulting from

interaction with the environment (adaptation)

Early Ideas About Evolution

Charles Darwin Discovery

As a naturalist on a voyage to South America 1831.

Biogeography

The careful observation and analysis of the geographic distribution of organisms

Suggested that organisms evolve from common ancesters.

Darwin's Voyage of Discovery

HMS Beagle was a 10-gun brig, 27.5 m long, that offered little room or comfort for the 74 people onboard

Darwin's Voyage of Discovery

Route of the five-year voyage of the Beagle

0 2000 4000 6000 km

What Darwin Observed?

Differences

between

closely

related

species human

whale

The forelimbs of these organisms are each adapted to carry out

very different functions, yet they all possess very similar bone

structure

Darwin’s Observations

Homologous features

Structures that share a common origin but

may serve different functions in modern

species

dolphin flippers and human hands

horse leg and wing of the bat

Darwin’s Observations

Analogous features

Structures similar in function but not in

origin or anatomical structure

wings of birds, bees and butterfly

eyes of lobster and fish

Homologous Features

salamander

chicken

pig

human

During Embryonic Stage

Vestigial Features and Anatomical Oddities

Vestigial features

Rudimentary and nonfunctioning structures that are homologous to fully functioning structures in closely related species

Dogs have a vestigial toe. Although the bones remain, this digit serves no

present purpose.

Pigs' feet have two well-developed digits; the others are vestigial.

Vestigial Features

Other examples in Humans

Humans have muscles for moving ears,

much as dogs and other mammals do

The appendix

Mechanism of Evolutionary Process

Artificial selection

A process to alter the appearance and

behavior of domesticated plants and

animals

Corn oil content dramatically increased in

only 60 generations

Evidence for an Evolutionary Mechanism

Darwin concluded that in the struggle for

survival

As species produce many more offspring

than can survive

there must be intense competition among

individuals in each species

the most favorable traits are inherited by

succeeding generations

Mechanism of Evolutionary Process

Natural Selection

Theory presented in 1858

Darwin postulated that natural processes

could act as agents of natural selection in

much the same way

Based on some basic observations and

inferences

Observations in Natural Selection Observation 1

Individuals within a species vary in many ways

Observation 2

Some of this variability can be inherited

Observation 3

Every generation produces far more offspring than can survive and pass on their variations

Observation 4

Populations of species tend to remain stable in size

Inferences in Natural Selection Inference 1

Members of the same species compete with each other for survival

Inference 2

Individuals with more favorable variations are more likely to survive and pass them on

Survival is not random

Inference 3

As these individuals contribute proportionately more offspring to succeeding generations, the favorable variations will become more common (This is natural selection)

Understanding Concept

Propose an evolutionary scenario in which a

species of ancient chameleons could evolve into a

species with an unusually long tongue

Understanding Concept

Keep in mind the two key elements

required for natural selection:

inherited variation

and

an environment that favors certain

traits over others

Summary of Natural Selection

All species exhibit inheritable variations that

are selected through the struggle by

individuals for survival in competition within

their population

Individuals with more favorable traits

produce more offspring that survive than

others and pass along those favorable traits

Summary of Natural Selection

Over many generations, this process results in

a change in the inheritable traits of the

population.

BRAIN STORMING!

When natural selection was first proposed,

scientists had no understanding of the genetic

basis of inheritance and variation

70 YEARS AFTER?

Mechanisms of Evolution

DISTINDUISHING TRAITS: These individuals exhibit variations, but they also share inherited physical features

The genetic diversity

is readily apparent

Genetic Variation

The genetic

diversity of

many

populations,

such as this one

of long-nosed

bats, may not be

readily apparent

to human

observers

Genetic Variation - Traits

RRTT RRTt RrTT RrTt

RRTt RRtt RrTt Rrtt

RrTT RrTt rrTT rrTt

RrTt Rrtt rrTt rrtt

Rt RT rT rt

RT

Rt

rT

rt

Parent

RrTt

Parent

RrTt

Genetic Variation

Trait

Changes in the individuals resulting from

interaction with environment

Genotype

The set of alleles possessed by an individual

organism

Phenotype

Observable trait of an organism that result from

interaction between genes and the environment

Genetic Variation

Homozygous:

Descriptive of a gene for which the paired

allele differ are identical

Heterozygous:

Descriptive of a gene for which the paired

allele differ

Genetic Variation

The quantity of DNA and the number of

genes are highly variable among species

Variation within a species is a result of the

variety and combinations of alleles possessed

by individuals

Sexual reproduction results in the random

recombination of often thousands of different

alleles and results in a high degree of genetic

diversity within most populations

Genetic Variation

Genes

portions of the DNA molecule within a chromosome coding for particular polypeptide products

Alleles

particular forms of a gene; many genes have two or more alleles

Population

all members of the same species living in the same region

Random Change

Evolution occurs when the allele frequencies

of a population change over time

Genetic drift and gene flow produce changes

in allele frequencies and affect genetic

diversity

The source of all new genetic information is

mutation

Random Change

Gene duplications are the maim source of

new genetic material. They are free to mutate

without the likelihood of causing harm

Although rare in individual cells, mutations

are numerous in large populations over many

generations

Random Change

Genetic drift

A changes in the genetic makeup of a

population resulting from chance

Such changes are much more pronounced in

small populations

Gene flow

The movement of alleles from one population

to another through the movement of individuals

or gamete

Genetic Drift The remaining

populations of the

endangered

Blanchard's cricket

frog, Acris crepitans

blanchardi, once found

on Pelee Island in Lake

Erie, are very

vulnerable to the

effects of genetic drift

Genetic Drift - Scenario

Large Population Scenario

Assume l in 50 cricket frogs carries a allele,

C1

Population of 10,000 individuals - 200 allele

Random deaths of half the population

about 100 of the 5000 survivors to be

carrying the C1

The allele frequency would not be

expected to change

Genetic Drift

Small Population Scenario

Population were only 100 individuals

only two to possess the C1 allele.

Random death of half the population

What is the chance?

both the C1 carriers would die- extinction OR

both would survive - doubling the allele frequency of C1.

When populations are small, chance can play a significant role in altering allele frequencies

Genetic Drift - Bottleneck Effect

When a sever event

result in a dramatic

reduction in numbers, a

population may

experience a bottleneck

effect

Bottleneck effect

a dramatic, often

temporary, reduction in

population size usually

resulting in significant

genetic drift

Genetic Drift - Bottleneck Effect

The northern elephant

seal population was

reduced by overhunting

to 20 individuals in the

1890s. Although the

population had

rebounded to over

30 000 individuals by

1974, genetic testing of

24 loci exhibited total

homozygosity

Mutation

Unrepaired changes in DNA sequence or

chromosomes breakage or rejoining

Mutations are random changes to the genetic code

Rare in individual cells, mutations are numerous in

large populations over many generations

Types

Neutral mutation

Has no immediate effect on an individual's

fitness, or reproductive success

Mutation Harmful mutation

Reduces an individual's fitness

Occurs when a cell loses the ability to produce a properly functioning protein or when major chromosomal changes adversely affect meiosis and mitosis

Beneficial mutations

Occurs when a cell gains the ability to produce a new or improved protein, gives an individual a selective advantage

Increased reproductive success

Mutations and Genetic Variations What is the source of variation?

How are subtle differences passed from generation to generation?

Scientific understanding of genetics and mutations answered these questions

Mutations provide a continuous supply of new genetic variations, which may be inherited and expressed as different phenotypes.

Natural selection leads to a variety of outcomes when this genetic variation occurs within competitive populations living under diverse environmental conditions.

Mutations and Genetic Variations Sickle-cell anemia, a blood disorder, is a useful

example of how mutation, genetic variation, and the environment result in different patterns of natural selection

The allele for sickle-cell anemia differ from the normal hemoglobin gene by having a single base-pair mutation

Homozygous individuals for the sickle-cell allele are severely afflicted with this disorder

Heterozygous individuals are only mildly affected by sickle-cell anemia however, they are much more resistant to malaria than are people with normal hemoglobin

Mutations and Genetic Variations Of the 120 million new cases of malaria each year, about 1

million are fatal. The prevalence of malaria in Africa (a) closely

matches the distribution of the sickle-cell allele (b)

Malaria

P. falciparum in Africa

1-50% 5-10%

10-20%

Adapted from Biology 5/E. fig. 20.4 p. 407 Peter H. Raven and George B. Johnson, the McGraw-Hill Companies, Inc.

Mutations & Genetic Variations - Outcomes

In regions where malaria is uncommon

Individuals with the sickle-cell allele are at a

disadvantage

Their phenotypes are less likely to contribute

alleles to the gene pool

In regions where malaria is common

Heterozygous individuals are at an

advantage

They are much more likely to survive and

pass on their genes to the next generation

Mutation and Evolution The environment selects the best-adapted phenotype and

favors a particular set of alleles

The sickle-cell allele is only common

where it provides an overall advantage to the individual

where it has an overall harmful effect, it does not persist

This pattern establishes an important relationship between mutations and evolution:

Harmful mutations occur frequently

but they are selected against

these mutant alleles remain extremely rare

Beneficial mutations are rare

but they are selected for

these mutant alleles accumulate over time

Sexual Selection

Sexual selection

Differential reproductive success that

results from variation in the ability to

obtain mates; results in sexual dimorphism

and mating and courtship behaviors

Sexual dimorphism

Striking differences in the physical

appearance of males and females not

usually applied to behavioral differences

between sexes

Sexual Selection

Individuals that mate and reproduce

frequently make a substantial contribution to

the gene pool of later generations

Sexual selection favors the selection of any

trait that influences the mating success of the

individual

The most common forms of sexual selection

result from female mate choice and from

male-versus-male competition

Sexual Selection

In some species, females choose mates based on physical traits, such as bright coloration, or behavioral traits, such as courtship displays and song

In other species, males are equipped with physical features that assist them in establishing control of and defending their territory against other males

This territory provides an area to which they can attract, and sometimes forcibly detain, the females with which they mate

Sexual Dimorphism - Advantage

Sexual

dimorphism

may take the

form of a

physical

advantage,

such as a much

larger size in

males, or an

enlarged limb,

as in fiddler

crabs

Sexual Dimorphism - Disadvantage

In some species of

penguin males and

females look so similar

that even they have a hard

time telling each other

apart

A male picks up a stone

and drops it at the feet of

a would be mate. If the

other penguin happens to

be a male, the gift is

firmly rejected

Sexual Selection - Detrimental

(a)

The mating game is risky for male tungara frogs. When calling for a mate in the dark, they run the risk of giving away their location to the deadly frog-eating bat.

What might change this situation?

Sexual Selection - Detrimental Sexual selection favors inherited traits that enhance

mating success but may reduce an Individual's chances of survival

Figure (a)

Avoiding predators is not made easier, for instance, by brilliant plumage or a distinctive song

Figure (b)

A bizarre extreme-sometimes called runaway selection

Although males and females both have eye stalks, females have preferentially mated with males with the longest eye stalks to the point where the feature has become very exaggerated

Cumulative Selection Evolution of a complex structure is a cumulative

process

Cumulative Selection

The accumulation of many small evolutionary changes over long periods of time and many generations, resulting in a significant new adaptation relative to the ancestral species

Adaptation

Any trait that increases an individual's ability to survive or reproduce compared to organisms that do not have the trait

Evolution of Complex Structures

Figure 1

The skin of this poison-

arrow frog produces

substances that are very

toxic. How might the

bright skin coloration of

such frogs have evolved?

Figure 3

The flamingo feeds on

tiny aquatic organisms

with its bill held in an

"Upside-down"

position. How might

this bill shape and

feeding pattern have

evolved?

Figure 2

Eyes positioned on the sides of

the head provide a wide field

of vision, more helpful for

detecting predators. This

primate has the trait of

forward-positioned eyes,

shared by humans, which

results in a very large blind

spot. How might forward

positioned eyes have evolved?

Evolution of Complex Structures

Rare beneficial mutations might have

occurred

Natural selection might have favored them

Adaptations produced accumulated one by

one

This slow process of cumulative selection

could have produced complex structures, such

as eyes, and continues to produce them

The Formation of New Species

Species

Members of groups or populations that

interbreed or have the ability to interbreed

with each other under natural conditions

Speciation

The formation of new species is a result of

the evolution of one or more reproductive

isolating mechanisms

The Formation of New Species

Reproductive Isolating Mechanisms

Any behavioral, structural, or biochemical

traits that prevent individuals of different

species from reproducing successfully

together

Geographic barriers are a cause of the

reproductive isolation of two populations

by allowing accumulation of differences in

mating systems

The Formation of New Species

Once two populations become reproductively

isolated, they no longer share mutations and

subsequent selection processes

Significant evolutionary changes that occur in

either population will result in differences

between the two gene pools, creating separate

species

Reproductive Isolating Mechanisms

Prezygotic mechanisms

Reproductive isolating mechanisms that

prevent interspecies mating and

fertilization

Ecological isolation,

Temporal isolation, and

Behavioral isolation

Prezygotic Mechanisms

Ecolological isolation Species that occupy separate habitats or separate niches of the same habitat do not encounter one another to reproduce (e.g. ground hogs in field & marmots in elevations)

Temporal isolation Similar plant species may bloom at different times of the day (e.g., day- and night-blooming cacti)

Behavioral isolation Each species may use different signals for attracting a mate. The mating behavior of male jumping spiders is an elaborate dance in which they shake their legs and wave their palps. Females of different species do not respond to the dance.

Reproductive Isolating Mechanisms

Postzygotic mechanisms

Reproductive isolating mechanisms that prevent maturation and reproduction in offspring from interspecies reproduction

Zygotic mortality

No fertilized zygotes or embryos develop to maturity

Hybrid inviability

Hybrid offspring are unlikely to live long

Hybrid infertility

Offspring of genetically dissimilar parents are likely to be strong but sterile. An example is ?

Hybrid Infertility - Mules

Modes of Speciation

Any series of events that results in the

reproductive isolation of two populations may

also lead to the formation of new species

Allopatric speciation

The evolution of populations into separate

species as a result of geographic isolation

Sympatric speciation

The evolution of populations within the

same geographic area into separate species

Allopatric Speciation

The Atlantic blue-

headed wrasse (a) and

the Pacific Cortez

rainbow wrasse (b) are

probably descendants of

a single species that

underwent allopatric

speciation after the

formation of the

Isthmus of Panama

separated the Atlantic

and Pacific oceans

(b)

Sympatric Speciation

Evidence strongly suggests that a number of species

of sticklebacks evolved by sympatric speciation

Question #1

Define speciation. Explain how the reproductive isolating mechanism affect speciation.

Speciation is the formation of new species as a result of the evolution of one or more reproductive isolating mechanisms

Reproductive Isolating Mechanisms

Any behavioral, structural, or biochemical traits that prevent individuals of different species from reproducing successfully together

Geographic barriers are a cause of the reproductive isolation of two populations by allowing accumulation of differences in mating systems

Once two populations become reproductively isolated, they no longer share mutations and subsequent selection processes

Significant evolutionary changes that occur in either population will result in differences between the two gene pools, creating separate species

Question #2 Define the following terms.

Genetic drift is a change in the genetic makeup of a population resulting from chance. Such changes are much more pronounced in small populations

Gene flow is the movement of alleles from one population to another through the movement of individuals or gamete

Genotype is the set of alleles possessed by an individual organism

Phenotype is the observable trait of an organism that result from interaction between genes and the environment