EVOLUTION

How populations evolve…

Charles Darwin…

Natural Selection…

Evidences and Mechanisms…

Evolution is merely a change over time.

• Considered the unifying theory of biology

• Like a family history only on a much grander scale

• Without evolution, all of us would look exactly as we did the day we were formed!

• Change over time allows us to progress from single cell to infant to adult!!

• Changes can be lifelong or seasonal.

Charles Darwin is considered to be the “Father of Evolution”

• Believed animals arose from ancestors…called this “descent with modification”

• Wrote The Origin of Species to explain HOW this happened

• Used voyage on the “Beagle” to document evidence

Darwin not the first to propose evolution…just the first to propose

a cohesive idea.• Aristotle and Judeo-Christian beliefs were that

species were “fixed” and didn’t change• Anaximander proposed life arose in water (it

did)• Buffon challenged that the Earth was young

(fossils helped prove much older)• Lamark proposed evolution…but…proposed

that by using or not using body parts changes occur…remembered for this and not evolution in general…Darwin gets all credit.

Things started to become clear to Darwin aboard the “Beagle”

• Collected specimens of plants and animals

• Observed adaptations of animals in different parts of the world

• Noticed many things in and around Galapagos Islands

• Many species found only here but resemble those found on SA mainland

• Adaptations included modified beaks of finches and necks of tortoise.

Darwin backed up his claim that living organisms evolve with

several Evidences:• Fossil Records—historical records of

organisms preserved in rock and sediment. Erosion of soil exposes the preserved specimens.– Younger specimens higher up in

rock layers– Footprints and other marks also

fossils– Fishlike fossils are oldest known– Paleontologist…one who studies

fossils.

Other evidences were biogeography…Animals more closely resemble those on same continent with different geography than those on distant continent with same geography.• Comparative Anatomy—

certain anatomical similarities between species bear witness to evolution. (human, cat, whale and bat all share same arm, hand and wrist bones)

• Comparative Embryology-comparison of different stages of development during embryonic development. For instance, all vertebrates have a stage where gill pouches are evident…in fish they become gills…in mammals they become a voice box.

One new evidence that has become important since the time of Darwin is Molecular Biology.

• Share similarities in DNA, protein sequences, genes and gene products.

• Common genetic code (same 4 bases, same 20 amino acids for all species)

• Genetic language passed along through all branches of evolution since day one.

• Allows us to produce mass quantities of vaccine, medicine and other important products through use of gene similarity across species. Yeast, viruses and bacteria all mass produce important medical products.

These tomatoes, developed by the Universityof Arizona, can produce a vaccine that helps develop immunity towards the HIVvirus that causes aids. You can also eat thetomatoes to obtain the vaccine.

Darwin’s observations led to his hypothesis that organisms change due to NATURAL SELECTION

• Most species will overproduce offspring leading to a struggle for existence in obtaining resources

• Variation within a population is inherited

• Differential reproductive success in population…those with “best” genes will produce more offspring.

Relative Importance of Natural Selection to Evolving Populations

• Struggle for existence helps “weed out” sick, weak organisms who cannot obtain resources

• Variation allows for some organisms to survive natural phenomenon because they have a different gene than those who don’t survive

Weeds with a natural resistance to herbicidesused to control them. Probably developed by passing genes of plants surviving repeated applications on to offspring.

Differential reproductive success means that animals who produce the most offspring are the most “fit,” meaning they have the “best” genes in the population to pass on to offspring allowing the offspring better survival chances.

Result of Natural Selection in Action

• Adaptation to the environment.• Organisms who are best suited for survival

and reproduction in the area they live in• Constant changes in environment mean

constant changes in organisms which allows for natural selection and adaptation to take place.

• How have you been forced to adapt since coming to SWOSU?

When humans interfere with Natural Selection disaster occurs!!

• Animals or plants selected for desirable traits but not necessarily those that allow them to survive in the wild

• Not allowing Mother Nature to do her job in controlling population numbers

• Larger populations of less desirable organisms or very “domestic” organisms

• Organisms specialized for only a single reason or use

Artificial Selection• "Less than 14,000 years

separates them: the wolf -the dog's ancestor- and the Maltese, one of hundreds of breeds of today's Canis familiaris. Humans transformed wild canines into the first domesticated animal -the tamable, trainable, incredibly variable dog." -National Geography, Karen E. Lang