Chapter 15-16 Evolution: Evidence and Theory Speciation
Let’s Go Back in Time!!
Eurypterids or sea scorpians
Amphibian Evolution (Change)
Ancestors Leave the Water!
The Most famous fossil
Transition between lizard to snake
Early Human Ancestors
Comparison of Early Humans
How have extinctions shaped our lives?
Extinctions Make Way for New Creatures! Precambrian Extinction Cambrian Explosion Huge diversity of shelled creatures Cambrian extinction New forms of hard-shelled creatures Ordovician extinction New creatures with bones and fish Land plants and forests Devonian extinction Amphibians and advanced fish Permian extinction (biggest) Cretaceous extinction Holocene extinction Dinosaurs! Mammals! What next?
Evidence for Evolution
Theories cannot be made without evidence.
One piece or one source of evidence is not enough.
1. Homologous and Analogous Features
2. Vestigial Structures
4. Macromolecules and DNA
5. Various Fossil Evidence and Transitional Forms
6. Seeing Evolution In Action
And much more……
The Fossil Record
A fossil is a trace of a long- dead organism.
Fossils are often found in layers of sedimentary rock.
Sedimentary rock is formed when sediment like dust, sand or mud is deposited and turns to stone over many years.
A mold is an imprint in rock in the shape of an organism.
A cast is when a mold fills in with hard minerals.
Sometimes a fossil can form when a whole animal is preserved in ice or sediment.
What can Fossils Tell Us?
Law of Superposition states that successive layers of rock or soil were deposited
The lowest layer is the oldest because it was deposited first.
Any fossils found in those layers would be around the same age as the layers.
Relative age is not exact but can only determine if a fossil is older or younger than another fossil.
Absolute age is determined using chemical processes which can show a number of years for the age of the fossil or rock layer.
Tooth marks on a fossil
Who is Tiktaalik?
Video segment Movie clip-chapter 5
Succession of Forms
Fossils indicate that species of organisms appeared, existed for a while and then disappeared or became extinct.
Mass extinctions occur when large amounts of species disappear.
Mass extinctions can be caused by the environment like volcanic activity or from asteroid impacts.
Current extinctions are being caused by humans.
Biogeography is the study of the comparison of fossils to living organisms.
Biogeography shows that new organisms arise in areas where similar forms once lived.
Modern coyote Extinct whales
Whale ear bones-found in no other living animals
Whales in the Making
Theories of Evolution (Change)
French scientist Jean Baptiste de Lamarck formed some of the first theories of change by observing animals with webbed feet and other animals like giraffes.
He thought that acquired traits like ones that are earned through life were passed down to offspring.
His idea was easily disproved but Lamarck was one of the first thinkers of change of his time.
Remember, Lamarck had the right idea but the wrong way about it! You can’t pass on a trait that you have acquired through life!
Darwin’s Dangerous Idea
In the mid-1800’s, Charles Darwin and Alfred Wallace independently developed an idea that species were modified by natural selection.
In the process of natural selection, organisms best suited to their environments reproduced more successfully than other organisms.
Over generations, the favorable traits increase in the population.
Voyage of the Beagle
Darwin rode aboard the ship the H.M.S Beagle as the ship’s naturalist so he could learn about all the plants and animals he found.
Darwin based some of his work on the research of Charles Lyell who said that many of the Earth’s geologic processes took a long time to complete and the Earth must be quite old.
Darwin observed high in the Andes mountains of South America that fossils of sea creatures were present. How did they get up there?
Darwin reasoned that the mountains must have been uplifted from the sea bed many years ago.
If the land can change why not the living creatures there?
Darwin collected many fossils and observed thousands of species on his 5 year journey.
The Galapagos Islands
Darwin visited the Galapagos Islands, an isolated part of South America.
There he observed many animals unlike those found on the mainland of South America.
Each island in the Galapagos had unique animals found no where else. Why?
Each island has a different variation that is adapted to that island only and found no where else. Each tortoise is genetically related to each other.
Darwin’s Observations More on Darwin. Movie clip chapter 2
Descent with Modification states that newer forms appearing in the fossil record are actually the modified or slightly changed descendents of older species.
Modification by Natural Selection states that the environment may affect individual organisms in different ways because they are not identical
Thomas Malthus said populations are limited by adverse conditions like war, famine and disease otherwise they would grow unchecked.
Darwin used Malthus’ ideas in his work.
A population of organisms adapt to their environment as their proportion of genes for favorable traits increases.
A single organism’s genetic contribution to the next generation is termed fitness.
A favorable trait gives an organism an adaptive advantage.
Mutations occur in species which can create favorable or unfavorable traits in certain environments.
stop Wait a minute….Isn’t Darwin’s Theory …just a theory? What is a theory anyway?
Homologous and Analogous Structures
A homologous structure is a similar feature that originated in a common ancestor.
These structures originate from the same areas in embryos of the animals.
Analogous structures are features that look similar because they are used for a similar purpose but arise from a different embryological development like wings in birds and bees
Vestigial structures are features that are no longer useful and have no apparent function in a current animal but had a function in a common ancestor.
Vestigial structures indicate common lineage.
Some animals like humans are born with vestigial structures showing like tails.
Whales have 4-chambered stomachs like a cow even though it is not used.
Wings in flightless and non aquatic birds
The human tailbone Blind fish with remnants of eyes that are not used
Human wisdom teeth Sexual parts in dandelions They do not use them; they clone themselves.
Virgin whiptail lizards clone themselves and no males are present in the species. The lizards still have sex even though it serves no purpose. Males have nipples and breast tissue although they serve no purpose. The human appendix is used in herbivores to digest plant matter but since humans are not herbivores, the appendix is not used.
Embryology is the study of embryos and their development.
Animals have similar embryos at certain stages of development indicating a common ancestor.
Guess the Embryo!
Macromolecules and DNA
All life on this planet has the same DNA bases and the same types of genes.
This indicates that we are all related.
Comparing genes and DNA, comparing amino acids sequences and comparing certain protein sequences all lead to the same conclusion…
As the number of differences decreases, the more related the two animals are.
If you take the gene for making an eye in a fruit fly and put that gene into a developing embryo for a mouse eye, it still produces a regular mouse eye. These are called homeobox genes and they control placement of appendages in all bodies of animals.
All Life is related!
Evolution in Action
Anyone can see evolution in action every day.
Entire populations can evolve into new species.
Larger animals take more time while bacteria and viruses can evolve in a matter of hours.
Guppies in high predator environments lessen their bright colors for defense. Over time the population becomes lighter and more drab in color. Why does this occur? Brighter colored fish are eaten more often and do not pass their genes to the next generation leaving only the drab colored fish to reproduce. Over time the population changes or evolves.
Patterns of Evolution
Coevolution is when two species change together in close association.
Some species cannot live without the other because they are so closely connected.
Convergent evolution is when the environment selects certain features to be similar even though the two animals may not closely related; sharks and dolphins
Divergent evolution is when two or more related populations over time become more different. This usually results in a new species; dogs and wolves.
Divergent evolution is also called adaptive radiation, when the animals adapt to a specific environment and change into new species over time.
Artificial selection is when humans select the traits and cause the evolution; dogs, cats, goldfish, grain crops
Coevolution The Yucca plant and Yucca moth, the plant is only pollinated by that moth. Lichens are a mixture of a fungus and an algae working together. They cannot live without each other.
Coevolution Many flowers like this snapdragon are designed specifically for a certain insect. Darwin actually predicted the existence of a certain moth by measuring the size of a flower opening. 40 years later, the moth was discovered!
Bees see in UV light and flowers evolved to maximize the bees visits by showing where the nectar is located. The flower’s colors glow and the landing strips show the bee where to go. Butterflies have a weak sense of smell. Flowers pollinated by butterflies are usually very fragrant and have bright colors like red or orange. Moths are nocturnal and do not need bright colors to feed. They need a long tube like flower.
This flower, the Rafflesia smells like rotten meat and poo. Who would pollinate this plant?
Flowers pollinated by bats.
Many marsupials have placental counterparts on other continents.
The environment selects an animal to occupy a habitat.
What is a species?
A species is a group of animals that can interbreed with each other and produce offspring that that also breed.
One species cannot breed with another and create offspring that can also breed.
There are many barriers that can restrict breeding which can contribute to the formation of a new species.
Speciation is the formation of a new species.
Isolating Mechanisms that cause Speciation
Geographic isolation is the physical separation of members of a population.
Examples are mountains, canyons, island creation, and separate bodies of water.
Reproductive isolation creates a barrier to successful breeding.
Examples are breeding times, breeding equipment, sterile offspring, mating calls and mating behavior
Many animals have variable genitalia so proper fit it necessary. This keeps species separated.