EVOLUTION

Charles Darwin

Question for Thought Earth has millions of other kinds of organisms of every imaginable shape, size, and habitat. This variety of living things is called biodiversity. How did all these different organisms arise? How are they related?

In your own words, describe what YOU think the theory of evolution means…

Darwin’s Theory of Evolution Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms. A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world.

How do you think Darwin came up with his theory?

Voyage of Beagle Dates: February 12th, 1831 Captain: Charles Darwin Ship: H.M.S. Beagle Destination: Voyage around the world. Findings: evidence to propose a revolutionary hypothesis about how life changes over time

The Galapagos Islands The smallest, lowest islands were hot, dry, and nearly barren-Hood Island-sparse vegetation The higher islands had greater rainfall and a different assortment of plants and animals-Isabela- Island had rich vegetation.

The Galapagos Islands Darwin was fascinated in particular by the land tortoises and marine iguanas in the Galápagos. Giant tortoises varied in predictable ways from one island to another. The shape of a tortoise's shell could be used to identify which island a particular tortoise inhabited.

Animals found in the Galapagos Land Tortoises Darwin Finches Blue-Footed Booby Marine Iguanas

Animals

The Journey Home Darwin Observed that characteristics of many plants and animals vary greatly among the islands Hypothesis: Separate species may have arose from an original ancestor

Lamarck

Population Growth Thomas Malthus-19th century English economist If population grew (more babies born than die) Insufficient living space Food runs out Darwin applied this theory to animals

Natural Selection & Artificial Selection Natural selection-differences among individuals of a species caused by nature Artificial selection- nature provides the variation among different organisms, and humans select those variations they find useful.

Evolution by Natural Selection The Struggle for Existence-members of each species have to compete for food, shelter, other life necessities Survival of the Fittest-Some individuals better suited for the environment

Natural Selection Over time, natural selection results in changes in inherited characteristics of a population. These changes increase a species fitness in its environment

Evidence of Evolution The Fossil Record Geographic Distribution of Living Things Homologous Body Structures Similarities in Early Development

We found the fossil — no joke! Land Mammal ? Complete series of transitional fossils ? Where are the intermediate fossils? ? ? There are innumerable intermediate & transitional forms Whales as land creatures returning to the water…. Where are the intermediate forms of whale ancestors? Cartoon making fun of this idea. The cartoons disappeared 10-12 years ago when this fossil was found. Ambilocetic natans = “Walking whale who likes to swim” 4-5 intermediate forms all found in last 2 decades Indus River valley in between India & Pakistan. Someone’s idea of a joke! Ocean Mammal But the joke’s on them!!

Evolution from sea to land 2006 fossil discovery of early tetrapod 4 limbs Missing link from sea to land animals

3. Anatomical record Animals with different structures on the surface But when you look under the skin… It tells an evolutionary story of common ancestors

How could these very different animals have the same bones? Compare the bones The same bones under the skin limbs that perform different functions are built from the same bones How could these very different animals have the same bones?

Homologous structures Structures that come from the same origin homo- = same -logous = information Forelimbs of human, cats, whales, & bats same structure on the inside same development in embryo different functions on the outside evidence of common ancestor

But don’t be fooled by these… Analogous structures look similar on the outside same function different structure & development on the inside different origin no evolutionary relationship How is a bird like a bug? Solving a similar problem with a similar solution

Analogous structures Dolphins: aquatic mammal Fish: aquatic vertebrate both adapted to life in the sea not closely related Watch the tail!

Because they used to walk on land! Vestigial structures Hind leg bones on whale fossils Why would whales have pelvis & leg bones if they were always sea creatures? Because they used to walk on land!

Vestigial structures Structures on modern animals that have no function remains of structures that were functional in ancestors evidence of change over time some snakes & whales have pelvis bones & leg bones of walking ancestors eyes on blind cave fish human tail bone

Comparative embryology Development of embryo tells an evolutionary story similar structures during development all vertebrate embryos have a “gill pouch” at one stage of development

Comparative Embryology

Figure 11.14 Comparative embryology. All vertebrates go through an embryonic stage in which they have four limb buds and a tail. From top to bottom: human, mouse, bat, chicken, and alligator embryos. Human

Mouse Figure 11.14 Comparative embryology. All vertebrates go through an embryonic stage in which they have four limb buds and a tail. From top to bottom: human, mouse, bat, chicken, and alligator embryos.

Bat Figure 11.14 Comparative embryology. All vertebrates go through an embryonic stage in which they have four limb buds and a tail. From top to bottom: human, mouse, bat, chicken, and alligator embryos.

Figure 11.14 Comparative embryology. All vertebrates go through an embryonic stage in which they have four limb buds and a tail. From top to bottom: human, mouse, bat, chicken, and alligator embryos. Chicken

Figure 11.14 Comparative embryology. All vertebrates go through an embryonic stage in which they have four limb buds and a tail. From top to bottom: human, mouse, bat, chicken, and alligator embryos. Alligator

3. Molecular record Comparing DNA & protein structure everyone uses the same genetic code! DNA 10 20 30 40 50 60 70 80 90 100 110 120 Lamprey Frog Bird Dog Macaque Human 32 8 45 67 125 compare common genes compare common proteins number of amino acids different from human hemoglobin

Building “family” trees Closely related species are branches on the tree — coming from a common ancestor

“descendants” of wild mustard Artificial selection How do we know natural selection can change a population? we can recreate a similar process “evolution by human selection” “descendants” of wild mustard

“descendants” of the wolf Selective Breeding Humans create the change over time “descendants” of the wolf

I liked breeding pigeons! Artificial Selection …and the examples keep coming! I liked breeding pigeons!

Artificial Selection gone bad! Unexpected consequences of artificial selection Pesticide resistance Antibiotic resistance

Insecticide resistance Spray the field, but… insecticide didn’t kill all individuals What caused the variation? mutation resistant survivors reproduce resistance is inherited insecticide becomes less & less effective The evolution of resistance to insecticides in hundreds of insect species is a classic example of natural selection in action. The results of application of new insecticide are typically encouraging, killing 99% of the insects. However, the effectiveness of the insecticide becomes less effective in subsequent applications. The few survivors from the early applications of the insecticide are those insects with genes that enable them to resist the chemical attack. Only these resistant individuals reproduce, passing on their resistance to their offspring. In each generation the % of insecticide-resistant individuals increases.

Any Questions??