BENCHMARK SC.912.L.15.1 Explain how the scientific theory of evolution is supported by the fossil record, comparative anatomy, comparative embryology, biogeography, molecular biology, and observed evolutionary change.
Evolution refers to change of species over time.
- In this unit you will learn about the process of evolution, its mechanisms, and the evidence.
In science, a scientific theory is the culmination of many scientific investigations, it accounts for many observations and data and attempts to explain and integrate a great variety of phenomena.
- Laws are well-supported descriptions
Scientific Theories are evaluated on the bases of
- A scientific theory represents the most powerful explanation scientists have to offer.
- Also remember that laws and theories are two complete different things. Theories will NEVER become laws or vice-versa.
- Laws are well-supported descriptions
Scientific Theories are evaluated on the bases of
- scientific argumentation
- critical and logical thinking
- and consideration of alternative explanations.
Evidence for Evolution
Evidence of evolution is available through:
A) Direct Observation of Evolutionary Change B) The Fossil Record C) Homologies or Comparative Anatomy, embryology, etc. D) Convergent Evolution E) Biogeography |
CPALM Tutorial: Evolution: Examining the Evidence
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A) Direct Observation of Evolutionary Change: When a populations reproduces so quickly, it is possible to observe the evolutionary process in short period of time.(micro-evolution)
- Insect populations can rapidly become resistant to pesticides such as DDT.
- Evolution of drug-resistant viruses, and antibiotic-resistant bacteria.
B) The Fossil Record
- Fossils are the preserved remains or traces of ancient life.
- The fossil record explains macroevolution.
- Macroevolution refers to evolution of groups larger than an individual species. Is evolution on a grand scale.
- Most fossils are preserved in sedimentary rock.
- Fossils provide evidence for the theory of evolution.
- Fossils show evidence that evolutionary changes have occurred over time. By comparing body structures in fossils to body structures in living organisms, researchers can infer evolutionary relationships and form hypotheses about how body structures and species have evolved.
- Fossils point at the origins of major new groups of organism.
- From the fossil record, paleontologists learn about the structure of ancient organisms, their environment, and the ways in which they lived.
- Fossils show evidence similarities between ancient extinct species and present ones.
Types of Fossils
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Transitional Forms in the Fossil Record
- Fossils or organisms that show the intermediate states between an ancestral form and that of its descendants are referred to as transitional forms. They provide evidence of how species have changed over time.
C) Homologies :
- A homology refers to as state of likeness due to common origen.
- Organisms share similarities derived from common ancestors:
- Structural Homologies: Anatomical signs of evolution, although the may have different functions.
I. Vestigial Structures:
II. Embryonic Homologies or Comparative Embryology:
- Comparative embryology is the branch of embryology that compares and contrasts embryos of different species. It is used to show how all animals are related.
- Early stages of animal development reveal anatomical homologies in embryos not present in adult organisms.
III. Cellular Homologies:
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IV. Molecular Homologies: Similarities in DNA, PROTEINS, CHROMOSOMES
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The picture below shows the similarities in amino acids of different species.
- Cytochrome-c is an important enzyme in the process of cellular respiration. It is a highly conserved protein in evolution of all species due to its indispensable function in the production of ATP.
Analysis:
•more differences in amino acids of cytochrome c means the less closely related
•OR fewer difference, more closely related
•more differences in amino acids of cytochrome c means the less closely related
•OR fewer difference, more closely related
D) Convergent Evolution: Explains why distantly related species resemble one another.
- Analogous structures arise from environmental pressure; having to adapt to similar environmental condition even though they do not share a recent common ancestor.
- Convergent evolution has take place when two organisms developed similarities as they adapted to similar environmental challenges, not because they evolve from a common ancestor.
- The likeness that results from convergent evolution are considered analogous rather than homologous.
- The torpedo shape of a penguin, dolphin and shark are the solution to move through an aqueous environment.
- Sugar gliders (marsupial mammals) and flying squirrels (eutherian mammals) occupy similar niches in their respective habitats.
E) Biogeography is the study of the distribution of species and ecosystems in a geographic space and through geological time.
- Species in a discrete geographic are tend to be more closely related to each other than to species in distant geographic areas
- Example: In South America , desert animals are more closely related to local animals in other habitats, that they are to the desert animals of Asia. This reflect evolution, not creation!
- Continental drift and the break-up of Pangea can explain the similarity of species on continents that are distant today.
- This type of evidence of evolution compares species living in different regions of the world.
- Many explorations have led to the conclusion that organisms migrate from a place of origin filling in different ecological niches. Overtime, under different environmental pressures, populations evolve to new species.
- An example of this is Darwin's finches. The finches show adaptive radiation because they adapted to the food sources of different islands that have a variety of limiting factors. Natural selection acted differently on each island, selecting the best adapted finch in each case.
Darwin's Finches: Adaptive Radiation
Mechanisms of Evolution
How populations evolve?
The 4 mechanisms of evolution are: A) Mutations B) Natural Selection C) Genetic Drift
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Whatch the following video to learn more:
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A) Mutations
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.Mutations are chages in DNA and can alter the allelic frequency in a population, but are rare.
b)Independent Assortment c)Random Fertilization |
B) Natural Selection
C) Genetic Drift
- In each generation, some individuals may, just by chance, leave behind a few more descendants (and genes, of course!) than other individuals.
- The genes of the next generation will be the genes of the “lucky” individuals, not necessarily the healthier or better adapted individuals.
- That, in a nutshell, is genetic drift. It happens to ALL populations—there’s no avoiding the whims of chance.
D) Gene Flow
- Also referred as "Gene Migration", is a mechanism for transferring genetic diversity among populations.
- Immigration and emigration (into or out of a population) may result in a change in allele frequencies (the proportion of members carrying a particular variant of a gene),
- Gene flows changes the distribution of genetic diversity within the populations.
Patterns of Evolution
Hominid Evolution
SC.912.L.15.10 Identify basic trends in hominid evolution from early ancestors six million years ago to modern humans, including brain size, jaw size, language, and manufacture of tools.
- A hominid is any primate of the family hominidae. Besides the modern species Homo sapiens, hominids also include extinct species of Homo (such as H. erectus) and the extinct genus Australopithecus.
Brain Size:
Primitive >>>>> Modern Human
Language:
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Manufacture of Tools:
Jaw and teeth Size:
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"Humans are possibly the weirdest species to have ever lived. We have freakishly big brains that allow us to build complicated gadgets, understand abstract concepts and communicate using language. We are also almost hairless with weak jaws, and struggle to give birth. How did such a bizarre creature evolve?"
Explore these excellent articles from BBC Earth
Explore these excellent articles from BBC Earth