EVOLUTION

How do we know about past life on Earth? Fossils- any evidence of prehistoric life, not necessarily just the remains of plants and animals. Found most often in: ice, tar, amber, casts, imprints, and petrification.

How do we know about past life on Earth? Examples include: Bones, Shells, Trails, Footprints, Burrows of Worms, Seeds, and even Spores of Fungi

You’re how old?...Dating Fossils Relative Dating- determined by the depth or position in the soil.

You’re how old?...Dating Fossils Absolute dating- using a radioisotope and half-life to determine the rocks age Half-life: the length of time it takes for half the radio-active atoms in a given sample to decay.

Evidence for Evolution Patterns of common descent are seen in classification. Internal similarities: Comparative: anatomy, biochemistry, embryology, DNA sequencing, fossil remains, convergent evolution, divergent evolution Evidence for Evolution

More Evidence for Evolution Vestigial organs: are remnants of once-useful parts. Homologous Structures: structures that have different mature forms in different organisms, but develop from the same embryonic tissues.

Even More Evidence Fossils

Evolution Theory Contributors Hutton- Earth and life are gradually changing. Malthus- organisms are producing more and faster then the number dying. Lyell- Earth is very old. Cuvier- organisms died as a result of catastrophic disasters

Evolution Theory Contributors Wallace- has same ideas as Darwin, doesn’t rush to publish…validates Darwin’s work Lamarck- theory of acquired characteristics (environmental pressures and internal desires bring on changes in the body).

EX. Giraffes necks grew longer as they tried to get food higher in the trees. Didn’t take into consideration that those with longer necks had an advantage. Lamarck example:

The more an organism used a specific body part, the better chances the offspring would get this feature or trait. Ex. A weight lifter, because the parent was large due to lifting weights, the offspring would be large too. More on Lamarck

Our Main Man…Charles Darwin Darwin was a naturalist and took a trip on the HMS Beagle- around the world in 5 years! Found a wide variety of organisms and stated: Change is inevitable over a period of time.

So….What is Evolution? Evolution- genetic change over a period of time Populations, NOT individuals evolve through mutations and genetic variations

Darwin referred to evolution as: descent with modifications: each living species has descended with changes from other species over time

Adaptations: physical and behavioral traits that allow and enable organisms to survive. Fitness: ability of an organism to survive and reproduce. (Passing genes to offspring.)

Trends All living species tend to over-produce Most seeds, eggs, or hatchlings die before they can reproduce All living species are extremely variable Many variations are inherited.

Selection in Nature… Individuals of the same species are different: some have slight advantages or disadvantages in the struggle for existence.

Selection in Nature… Struggle for existence- high birth rates and shortage of life’s basic needs forced organisms into a constant struggle for existence. Competition! The fastest predators could catch the most prey The best camouflaged, protected or fastest prey survived the hunt.

Selection in Nature… Natural Selection- generation after generation the fittest individuals survive in nature. This explains how well-suited species become better suited to their environment as they respond to the various selection pressures.

Evidence for Natural Selection All living things are highly adapted to their way of life. Many adaptations cannot be explained by environmental influence. Some adaptations are less than perfect. NS has been observed and has resulted in changes in natural populations. Artificial selection by “breeders” has produced many new adaptations

No two alike…. Farmers told Darwin that no 2 individuals (plants or animals) were alike, some were larger, smaller, lighter, heavier, produced more milk, produced larger fruit, etc…. They knew that the traits were inheritable (Mendel), and they also knew what to do with these individuals when they found them…

No two alike…. Farmers would look over their stock and decide what characteristics they wanted to see in the next generation…they would select them…. Artificial Selection- allow only certain organisms to reproduce to obtain certain results (characteristics) in offspring.

Darwin’s Finches On the Galapagos Islands, Darwin found many different birds that were seed eaters with different beaks. Darwin found out, after some observations, that all the birds were not different species, but all Finches.

Darwin’s Finches The finches (no matter how different they looked) all evolved to have different beaks so that they could all survive on the island by maximizing food resources. (If they all ate the same seeds, there would be a food shortage so over time some took to eating fruit, insects, seeds…. They could all survive.)

Evolution of a Species Species are evolutionary units in which gene flow occurs. Natural populations belong to the same species if they can interbreed and leave fertile offspring. Most new species originate geographically when interbreeding populations are isolated for long periods of time and the gene pool remains within the group of that habitat.

Reproductive Isolating Mechanisms 1. Ecological isolation occurs when potential mates do not meet because they are in different habitats.

Reproductive Isolating Mechanisms 2. Seasonal isolation is when potential mates breed at different seasons or at different times.

Reproductive Isolating Mechanisms 3. Behavioral isolation might occur when mating courtship is different.

Reproductive Isolating Mechanisms 4. Mechanical isolation occurs when the reproductive structures do not match up properly.

Genetic Drift Migration- the movement of organisms through a geographical area. Immigration- INTO a geographical area Emigration- OUT OF a geographical area

Genetic Drift Directional movement- a shift in a population to 1 side; either the right or the left

Genetic Drift Disruptive movement- a shift in a population to both ends decreasing the number in the middle.

Genetic Drift Stabilizing movement- a balancing out of populations evenly through the species.

Natural Selection may be Disturbed by Man Destroying natural habitats Endangered species Extinct species

Scientists estimate that between 5 and 50 million different species make the Earth home. Remember: a species is a group of organisms able to reproduce viable offspring

Scientists estimate that 99 Scientists estimate that 99.9% of all species that have ever lived are now extinct. How do we survive?

The Problem of Reproduction Back to Malthus- 1788, observed that babies were being born faster than people were dying. If this continued, the world would be overrun by humans. So Malthus suggested that war, famine, and disease would limit the human population (stress on the environment)

Why evolution… In relating evolution to physics, everyone knows that gravity works although it is very hard to understand why it does, the same goes w/ evolution and biology. Evolution explains why bacteria become resistant to antibiotics, and why insects become resistant to pesticides.

Why evolution… Inheritable variation (through evolution) is essential to species survival.