6 Evolution.pptx

What is evolution?

The central and unifying theme of biology

The term “evolution” means gradual change over time

Geologic evolution: the slow, continuous change of the earth itself

Evolution

is the process by which

one species gives rise to another.

Confusion sometimes arises as to whether Evolution is a theory or a fact.

The theory of Evolution deals with how Evolution happens. Theories in science explain phenomena.

Evolution is also a fact as there is a huge amount of

Misconceptions about

Evolution

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Pope Francis has said:

imagining that God was a magician, with a magic wand which is able to do everything. But it is not so. He created beings and let them develop according to internal laws which He gave every one, so they would

develop, so they would reach maturity.”

Fossil: a trace or remains of an organism that has been preserved by natural processes

Mostly the hard parts (bones and shells) are preserved

Fossils allow paleontologists to date the organisms The layers of sediment in which the fossils are

formed can give some idea of relative dating

Problems with Fossil

Records

Fossils rarely form; most organisms either decay completely or are consumed

Fossils that do form rarely survive long enough for us to find them

Fossils are rarely accessible – they are buried too deep for us to find

2. Comparative

Anatomy

Comparative Anatomy refers to the

structural similarities and differences

between living things.

Similar structures in different organisms

points to similar ancestry. The more

Homologous Structures

Parts of different organisms that have

similar structures, but different forms or

functions.

Analogous Structures

Different organisms have organs with the same function, but different underlying structure.

They are thought to be evidence for evolution along two different lines.

Vestigial Structures

FYI…

Humans have over 100 vestigial structures!

◦

_{Coccyx (tailbone)}

◦

_Appendix

◦

_{Wisdom Teeth}

◦

_Goosebumps

◦

_{Infant grip reflex}

◦

_{Muscles to move nose and ears}

Embryological

Similarities

Closely-related species have similar patterns

of development

In embryonic stages, homologous structures may appear that may not appear in the adult forms of two organisms

For example, humans have a very early stage in utero with gill-slits. This points to a common ancestor with fish.

Humans also have a tail for much of their

Molecular Similarities

Due to genome sequencing, we can now examine similarities in DNA

Because every organism inherits DNA from

their ancestors, the DNA of every living

comes originally from the earliest forms of

life

Cytochrome c

One protein, which is needed for cellular

respiration, is called Cytochrome c.

Because of mutations in DNA,

Differences among cytochrome c are more

pronounced the further back a common

ancestor between two species is (the longer

ago the species diverged)

Cytochrome c

comparisons

Humans and chimps – 1 amino acid differs

Humans and pigs – 10 amino acids differ

Jean Baptiste Lamarck

Was convinced that species were not constant

Thought that changes in

First Principle: Law of

Use and Disuse

◦

_{The more an animal uses a specific part of}

their body, the stronger and

better-developed that part becomes.

◦

_{The less a part is used, the weaker and}

Second Principle:

Inheritance of Acquired

Characteristics

Characteristics that an organism acquires

Classic Lamarck

Example

Giraffe’s long necks:

◦ _{Lamarck knew the ancestors of modern giraffes}

had short necks

◦ _{He thought they would have run out of grasses}

and low leaves to eat and had to stretch their necks to get food

◦ _{Over time, the stretching resulted in their necks}

getting longer

Charles Darwin

Son of a physician who wanted him to study medicine

Went on a voyage on the HMS Beagle in 1831, which lasted 5 years. He returned convinced that organisms evolve.

Made many observations of plants, animals, and insects

Made his most significant

Darwin’s Book

On the Origin of Species by Means of Natural Selection

Darwin’s Influences

Charles Lyell: The Principles of Geology. This proposed the earth was very old and changing over time (Geological Evolution)

Thomas Malthus: An Essay on the Principle of Population. This proposed that human food supply could not keep up with the growing population, leading to death by disease and starvation.

Darwin’s Theory of

Natural Selection

Read the text pages 420-421

Complete the worksheet

For the examples use the giraffe. How would

Darwin’s theory of evolution by natural

Hugo Marie de Vries

1848-1935

Dutch botanist and geneticist

Rediscovered the Laws of Heredity in 1890, without having read

Mendel’s work

Mutation Theory

Introduced the term “mutation” to describe

suddenly-appearing varieties of plants

Argued that new species are not formed by

continuous variations, but by sudden

Alfred Wegener

1912

Alfred Wegener proposed the theory of

continental drift – the idea that Earth’s

continents move. Despite publishing a large

body of compelling fossil and rock evidence

for his theory, it was rejected by most other

scientists. It was only in the 1960s that

August Weismann

1834-1914

Studied chromosomes

Was not convinced of

Lamarck’s theories and did experiments to disprove them

Weismann’s work formed the basis for Modern Synthetic Theory and provided an important link between genetic material and natural selection.

Evolution Heredity

Lamarck (Use + Disuse)Mendel (Inheritance)

Darwin (Natural Selection) de Vries (Mutations)

Weismann

Theodosius Dobzhansky

1937

Author of Genetics and the Origin of Species, a book that offers an explanation for how species actually came into existence.

Mutations crop up naturally all the time. Some

Modern Synthesis

Dobzhansky's ability to combine genetics and natural

history attracted many other biologists to join him in the effort to find a unified explanation of how evolution

happens. Their combined work, known as "The Modern Synthesis," brought together genetics, paleontology,

E. O. Wilson

1975

SOCIOBIOLOGY: THE NEW SYNTHESIS

Wilson used sociobiology and evolutionary principles to explain the behavior of social insects. He argued that all animal behavior,

including that of humans, is the product of heredity,

environmental stimuli, and past experiences, and that free will is an illusion.

The sociobiological view is that all animal social

behavior is governed by

Microevolution vs.

Macroevolution

Microevolution: the evolution of a

species as the environment changes.

Microevolution: Dogs

are Wolves!

The dog is example of how selection can change the

frequency of alleles in a population.

Dogs have been artificially

selected for certain characteristics for many years, and different

breeds have different alleles.

All breeds of dog belong to the same species, Canis lupus (the wolf) so this is an example of

Macroevolution:

Darwin’s Finches

However, if two populations of a species become isolated from

one another for tens of thousands of years, genetic difference may become marked.

If the two populations can no-longer interbreed, new species are born. This is called Macroevolution.

Darwin’s Galapagos finches are

Speciation

Species:

Group of organisms that are structurally similar and naturally interbreed to pass similarity on to offspring

Speciation: Refers to the formation of a new species.

Reproductive Isolation

Is what keeps members of one population

from interbreeding with members of

Barriers to reproduction and

recombination between species:

Pre-mating Barriers: Prevent mating from

occurring between two organisms of

different species.

Geographical Isolation

Divided by a natural barrier

◦ _{Ocean, mountain, desert, river…}

◦ _{e.g. Until very recently polar bears and grizzlies}

Ecological Isolation

Animals inhabit different habitats

◦ _{For example, white-crowned sparrows live in}

Temporal Isolation

Different species breed at different times of

the year.

Behavioural Isolation

Courtship and mating rituals differ, so that members of different species won’t

interbreed.

◦ _{E.g. Female songbirds}

only respond to the song of a male of the same species.

◦ _{Blue-footed booby dan}

Mechanical Isolation

Reproductive structures between two species are incompatible.

Gametic Incompatibility

Sperm of one species cannot fertilize

egg of another

Hybrid Inviability

The hybrid (result of mating between

different species) does not survive to

adulthood.

E.g. It may show behavioural traits of both

parents, which are incompatible with each

other

Hybrid Infertility

Species which are similar can often reproduce. If, however, they have a different chromosome

number, this poses problems.

With unequal numbers of chromosomes

Following isolation…

Isolating a group of organisms separates its gene pool from the rest of the species.

Following that, mutation, genetic recombination, and natural selection can cause a different gene pool to evolve .

Adaptive Radiation

Refers to species spreading or radiating out

into different environments.

Each species will adapt to the pressures in its

own environment.

Other Patterns of

Evolution

Coevolution

The Rate of

Speciation

Gradualism

According to Darwin’s theory, new species arise

through gradual accumulations of small variations. Evolution proceeds slowly and smoothly over

millions of years

Punctuated Equilibrium

Supported by the work of de Vries

Punctuated Equilibrium

change in their geological history. Stasis: a state where a species remains unchanged for a long period of time

Evolutionary change happens in a rare and rapid bursts

Fossil Record says…

Gradualism

◦ _{Transitional forms are}

lost due to rarity of formation of fossils

◦ _{Leads to the observed}

gaps in phylogeny

Punctuated Equilibrium

◦ _{Transitional forms are not}

lost; they don’t exist

◦ _{The jumps observed in}