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Transcript of Chapter 6
The Process of Evolution
Fossils and Evolution 6-1
Biological Evidence 6-2
Comparative Anatomy is another form of evidence that supports the theory of natural selection. It is the study of the differences and similarities between the structures of evolution.
Many important scientific discoveries have been made using comparative anatomy.
Geographic Isolation is when landforms become barriers between populations of species. Landforms are created when lithospheric plates move.
When the lithospheric plates move apart, features such as valleys are formed. When the lithospheric plates move together, features such as volcanoes and mountains are formed.
Some geographic features that can lead to geographic isolation are: rivers, large bodies of water, valleys, volcanoes, and mountains.
Fossils and Evolution
Evolution and Plate Tectonics
Classifying Organisms 6-4
What You Will Learn
What are fossils?
Fossils are naturally preserved remains, imprints, or traces of organisms that lived long ago, including bones, shells, and footprints.
Paleontologists, a scientist who studies fossils, study fossils to determine the relationship among organisms, when different organisms appeared on Earth, and when they became extinct.
Some paleontologist work on uncovering fossils outside and others work in laboratories analyzing and learning about fossils.
Aristotle, a Greek philosopher was the first one to classify organisms. He categorized things as animals, plants, or minerals. He also grouped them by where they lived, whether it was air, land , or sea. A Swedish botanist know as Carolus Linnaeus grouped different organisms based on their physical structures.
Evolution and Plate Tectonics 6-3
The hypothesis of continental drift was proposed by Alfred Wegener in 1912. The most obvious evidence for his hypothesis was the fit of the shorelines of Africa and South America.
As the lithospheric plates move, environmental changes result for the species that live there. Natural selection for these species occurs when the environment changes.
Structures in living Organisms
Birds, cats, humans, frogs, and bats all have a common set of three bones in their front or upper appendages. The bones are all different sizes, but the forms are similar. This means they all shared a common ancestor at one point. Some happen to be more recent then the others.
How are fossils formed?
Scholars once thought that the bones and teeth of once-living animals magically turned into stone. Scientists figured out how fossils formed in the seventeenth century.
Fossils only form under certain conditions, which are usually formed on hard structures, and sometimes soft structures as well. There are many ways of different methods of preservation.
The Different Types of Structures
There are three different types of structures. They are called homologous structures, analogous structures, and vestigial structures. They all serve different needs and purposes.
Cell type, the presence of a cell wall, or whether organisms are single-celled or multicellular, are used to define a kingdom. There are six different types of kingdom:
and Kingdom Amilia
When do fossils form?
The decomposition process is part of an organisms life cycle. Worms, insects, bacteria, fungi, and other organisms help the decomposition process by breaking down the dead organisms. There is a chance that scavengers might eat parts of the dead organism, and scatter what they can't eat.
In order for dead organisms to become fossils, they must be well protected from scavengers, decomposers, and environmental factors, such as acidic soils or heavy rains. Also, teeth, shells, and bones of an organism has a better chance of survival rather than not having a hard structure, and organisms are less likely to eat hard structures.
Modern Methods of Classification
The modern study of classification is called
DNA and molecular biology are both used to identify relationships between organisms. Do do new advances in modern science, scientists can now determine the sequence of the molecules in an organism's DNA.
If two organisms share similar DNA, then they probably both came from similar ancestors. Scientists can also determine the sequence of a sample of 1,000 molecular pairs in DNA called haplotypes. They compare these haplotypes to detect signs of similarities in organisms. A new level of classification developed from molecular biology is domain. Domain is now the highest level rather than kingdom. There are three domains:
Hard structures of a living organisms contain tiny spaces filled with blood, air, and other substances is buried layer of sediment slowly begin to compact and cement to form rock. During this process permineralization is when the water in the ground seeps into the tiny empty spaces and deposits minerals then forming a strong rock like fossil. An example of this process are fossilized trees referred as petrified wood.
Embryology is the development of embryos from fertilization to birth. Some scientists study the embryology of different animals and compare and contrast the patterns of development. Similar patterns can provide clues.
Darwin's Observations of Geographic Isolation
When a dead organism is quickly buried with conditions were there isn't any oxygen, other elements normally found in living tissue like, hydrogen, oxygen, and nitrogen are removed. What is then left is a thin film of carbon. When a carbon film forms, which preserves the image or shape of the original organism on a rock, when pressure from built-up sediment compresses the buried organism. In carbon films, soft materials can be preserved, such as skin, fur, and feathers. In coalfields many of these fossils may be found.
Many of the species in Charles Darwin's journals were part of geographic isolation at one point in time.
The results of geographic isolation puzzled Darwin. This made him more inspired for his research.
He noticed that species on the Galapagos Islands were more similar to those on the Ecuador mainland, despite the differences in their environments. The similar organisms were clearly unique species. These observations by Darwin led to the idea of evolution by natural selection.
An example of original material would be an organism preserved in amber, which is considered a type of fossils. An original material fossil is one of a kind,because none of the hard or soft structures have been altered or replaced. An example of original material would be a frozen head of a wooly mammoth. It is very rare to find original material, but it gives a lot of information to scientists. Unlike other fossil types original-material fossils are much more recent.
Molds and Casts
A mold or cast is a preservation of an impression or indentation of an organism. An example of a mold would be imprints from the skin of an animal or a shell. Molds can also include footprints, bite marks, and eggs in a nest. No remaining parts of the original organism can be found in these fossils. If a mold is hardened into rock by filling sediment into it, a cast fossil forms.
What do fossils tell us?
Fossils tell much of the evidence for the pattern of evolution and evolutionary relationships. To study process and rates of evolution is another reason that scientists study fossils. A record of different species that lived in the past is provided by fossils.
A microfossil is a fossil that is seen by a microscope.
Relative Fossil Ages
Generally, the deeper a rock layer is in the Earth, the older it is. If a paleontologist discovers a fossil in a shallow sedimentary rock, then finds another, but in a deeper sedimentary rock layer, the older fossil is usually in the deeper sediment
Unless there has been unusual disturbance that has rearranged the rock layer, ages of fossils can be compared by the relative ages of rocks.
All known fossils and their placements in the formation of rocks and position in time is known as the fossil record. Just like missing pages of a story book the fossil record has many gaps in it.
Fossils help scientists learn about complexity of life, comparing it from the past, and today. To see what these animals look like, scientists make models of the organism, and can find out what animals ate, if they lived in groups or alone, and the environment they lived in, etc.
5 steps to fossilization of a shell
Shell falls into the mud.
The shell buried in sediment.
100-1,000 years shell goes under layers of sediment, which turn into rock
Water and air reach the shell and dissolve it.
Shell then turned into fossil, and found.
Thanks for Watching!
By: Mona Miraftab, Ava Meyer, Lucy Levine, and Noah Hecht
One Big Jigsaw Puzzle
When you look at a world map, all the continents look as if they could fit together. This is because they once did. Wegener proposed that all the continents once fit together into a single landmass. Nowadays, we call this landmass "Pangea."
Visualizing Geographic Isolation
In Southern California, salamanders can't successfully interbreed. Presently, they are classified as one species. Over time, this
species might become two distinct species of salamanders.
This is a carbonized fossil
Replacement has similarities to permineralization, because in both processes includes critical minerals such as, silica, iron and pyrite. In replacement the hard structures dissolve and get replaced by minerals. Then the only thing that remains of the organism is its shape
To the right is a diagram that shows the classification levels for a leopard.
Homologous structures are the result of evolution. They can also indicate how closely two specie's ancestors are related and if they share a common ancestor at all.
Analogous structures are when two species are similar in how they function, but the structure of the features is different, just like the wings of birds and insects.
Vestigial structures are another source of evidence for evolution. They have no function in their present day form. How ever the scientists think that they had a function in our ancestors.
Linneaus also developed a system for naming species, and is still used today. The two-word scientific name of an organism is its species name. For example, the western spotted skunk's species name is Spilogale gracilis. The groups of similar species belong to a genus. The first word word of the specie's name identifies its genus. So the genus for the spotted skunk is Spilogale.
the similar genera (plural for genus) belong to a family
the similar families belong to an order
the similar orders belong to a class the similar classes belong to a phylum (plural phyla) and
the similar phyla belong to a kingdom.