Evolution Change over time 1 Jean Baptiste Lamarck
Evolution Change over time
1. Jean Baptiste Lamarck wrote of evolution before Darwin but his explanations for it were incorrect.
His ideas were: a. organisms are born with a desire to change. (the ancestors to birds wanted to fly) b. Organisms could change their shape by using their body differently (flapping your arms would lead to your arms becoming wings) c. acquired traits are inherited (giraffe example)
Giraffes got long necks by stretching them to reach food Over time their necks got longer. That trait was then passed on to their offspring.
2. Thomas Malthus He studied populations. He predicted the end of the world based on when the number of people would be greater than the resources
Darwin thought this applied to plants and animals more than humans. Other species produce more offspring than humans. Most of those will die.
3. James Hutton-geologist Published an idea about the forces that have shaped the earth. These processes take a long time so the earth must be millions of years old.
4. Charles Lyell-geologist Said the processes acting on the earth are still happening. These processes include earthquakes, volcanoes, erosion, etc. Darwin reasoned that this would apply to organisms as well as the earth.
5. Charles Darwin-(1809 -1882) Well educated Interested in natural history graduated from college and took a job as a naturalist on a ship. The ship was called the Beagle and would be gone for 5 years sailing around the world.
On this journey Darwin made observations and collected evidence that led him to theory of evolution.
Voyage of the Beagle
Several years after his voyage he wrote his book called “On the Origin of Species”
His ideas included: a. Organisms have variations and these are inherited. b. Artificial selection occurs when the best organisms are selected to mate c. Natural selection occurs when nature selects the best to survive
d. Organisms struggle for existence or compete for resources. e. The ability to survive and reproduce is the organism’s fitness. Organisms with the best traits suited for their environment will survive, those not best suited will die. This is called survival of the fittest.
f. Descent with modificationsover time a species will change and not longer look like its ancestor.
g. Common descent-all species both living and extinct came from a common ancestor.
Evidence that supports evolution: 1. Fossils-are the remains of ancient life. Different layers of rock were formed at different times in earth’s history. Examining fossils will show a species changed over time.
2. Geographic distribution unrelated organisms on different continents will evolve to be similar if their environments are similar Related organisms will evolve to be different if their environments are different.
3. Homologous structures-similar structures on different organisms that have different purposes. Example: arm bones of bat, human, horse and frog.
4. Vestigial organs-structures that have lost their purpose. Examples: tailbone, appendix, ear muscles
5. Embryos-the embryo is the early stage of development in the organism. Many embryos look similar which shows they have similar DNA.
Examples of natural selection 1. Camouflage-blending in with the environment
Example: peppered moths In early 19 th century England oak trees had light bark, moths that were light in color were camouflaged and not eaten, dark ones were easily seen and eaten by birds.
In London after the industrial revolution the trees were covered with soot from coal and turned dark. Now the moths that were selected to survive were the dark ones.
2. Mimicry-looking like something else to avoid being eaten. a. Some try to look like something harmful example: Monarchs and viceroy butterflies b. Some harmful organisms look alike to increase the message that they are bad example: ants, bees, wasps with yellow and black stripes.
Monarch and Viceroy good tasting one copies the bad tasting one
Another example of a harmless copying a harmful
Making the message to avoid “stronger”
3. Isolation-a species becomes reproductively isolated so that they cannot mate with each other. There are 3 types:
a. Behavioral isolation https: //www. youtube. com/watch? v=w. Tcf. DCj. Bq. V 0
b. Geographic-two populations are created by a physical barrier Example-Grand Canyon squirrels. They were originally the same species. They were isolated from each other when the canyon grew deeper and now they cannot mate with each other.
Another example
c. Temporal- two species reproduce in the same area but at different times of the year. Frog on the left mates January to February Frog on the right mates March to May
Evolution and genetics A population is a group of the same type of organisms in the same area. Gene pool is all the genes found in the population.
Frequency is the number of times that a gene occurs in the population.
Sources of variation: 1. Mutations-a change in the DNA sequence. Mutations can effect an organism’s ability to survive
2. Gene shuffling-independent assortment and crossing over, which occurs during the formation of egg and sperm cells.
Natural selection works on phenotypes not genes. Phenotypes will often fit a bell curve when graphed.
Stabilizing-graph shifts inward
Directional-shifts toward one extreme
Disruptive-shifts to both extremes
Genetic drift-random changes in gene frequency, occurs just by chance. example-a small group leaves a large population and moves to a new area to colonize. Their genes may not represent the whole population they came from so they evolve differently.
Gene flow-migration into or out of a population brings in new traits or may eliminate others.
How fossils form: 1. an organism dies 2. it is covered by layers of sedimentary rock 3. it’s tissues are slowly replaced by minerals 4. it is uncovered.
Relative dating-determining the age of a fossil by comparing its depth with that of other fossils in the area. Radioactive dating-Some elements in rocks are radioactive. These will decay at a predictable rate. Measuring the rate of decay can determine the age of fossils in the rock.
Geologic time represents evolutionary time. It is based on rock layers and fossils. The Eras are Paleozoic, Mesozoic and Cenozoic. Periods divide the Eras into smaller time units
Extinction-death of species, they occur naturally all the time. 99% of everything that has lived on the earth has gone extinct. Mass extinction-huge numbers disappear at the same time
Adaptive radiation: A single species evolves into several forms.
Convergent evolution: unrelated organisms evolve to look like each other
Co-evolution: two organisms evolve to depend on each other closely. Examples: wasp and orchid cuckoo and warbler
How quickly does evolution takes place? Gradualism-changes are slow and steady through long periods of time. Punctuated equilibrium-long periods of time with no evolution and then big changes occur.
Cladistics/Phylogenetic trees Phylogeny is the ancestry of organisms. Comparing traits to determine the order in which groups of organisms branched off from their common ancestor.
Speciation event-the ancestral species splits into two new species. Each successful event creates a new branch. The bottom represents the ancestral species. The pattern of the branches represents the degree of relationship among the organisms. Derived characters-traits shared only by members of one branch or clade—they are unique to that group.
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