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Transcript of HCCC-Prin.Bio.II- Evolution
Descent With Modification
Overview: Endless Forms Most Beautiful
• A new era of biology began in 1859 when Charles Darwin published The Origin of Species
• Darwin noted that current species are descendants of ancestral species
• Evolution can be broadly defined by Darwin’s phrase descent with modification
• More specifically, evolution is the change in genotypic frequency of a population over time.
DNA - The Character of Inheritance
It's a fact that DNA is the character that connects the "Unity in Life" and the "Diversity in Life"
The earth is a gradually changing biosphere, demanding it's inhabitants to adapt to the environment she decides to present
Physical forces drive the cycles that create conditions, in which the organisms that are most suited, will survive
The Evolution of Populations
The smallest Unit of Evolution
1977, drought decimated the Geospiza fortis population on the island of Daphne Major
Of some 1,200 birds, only 180 survived
Of the 1,200, the 180 that survived had deeper beaks and could feed on the harder shelled seeds that were more plentiful
The allele for deeper beaks were passed on the next generation
The allele was passed to individuals of the population which in subsequent generations carried the trait. The population evolved, not the individual
Genetic Variation Makes Evolution Possible
Darwin realized that variation in heritable traits is the prerequisite for evolution
Gregor Mendel wrote on the inheritance in pea plants
Mendel proposed a model of inheritance, "unit of inheritance" now known as genes
Genetic Variation Drives Evolution
Genetic variation by "either-or" basis - Mendel's pea plant flower phenotype
determined by a single gene locus
Other phenotypic differences vary in gradations along a continuum, multiple genes, multiple loci
Important to understand that some phenotypic variations are not heritable
In general, only the genetically determined part of phenotypic variation can have evolutionary consequences
Sources of Genetic Variations
The genetic variation on which evolution depends originates when there is a:
Or other processes produce
Production of New alleles or new genes
Altering Gene Number or Position
Chromosomal rearrangements create variation
Translocation of sections of a chromosome
Duplications of genes during meiosis
The remote ancestors of mammals had a single gene for detecting odors that has since been duplicated many times. As a result humans today have about 380 functional olfactory receptor genes, mice have about 1,200
Mutation rates tend to be low in plants and animals, averaging about one mutation in every 100,00 genes per generation
Even lower in prokaryotes, but prokaryotes have many more generations per unit of time, so mutations can quickly generate variations within populations of prokaryotes
In organisms that reproduce sexually, most of the genetic variations in a population result from the unique combination of alleles
Sexual reproduction shuffle existing alleles and deals them at random to produce individual genotypes
Three mechanisms contribute to sexual mutations:
Fertilization - Segregation
New alleles can arise by mutations, a change in the nucleotide sequence of an organism's DNA
Hemoglobin is a protein found in red blood cells, and is responsible for the transportation of oxygen through the body. There are two subunits that make up the hemoglobin protein: beta-globins and alpha-globins. Beta-hemoglobin is created from the genetic information on the HBB, or "hemoglobin, beta" gene found on chromosome 11. A single point mutation in this polypeptide chain, which is 147 amino acids long, results in the disease known as Sickle Cell Anemia. (147 amino acids = 3 nucleotides per amino acid = 441 nucleotides long)
Point mutation: a mutation affecting only one or very few nucleotides in a gene sequence.
A human brain weighs in at about 1,500 grams, huge compared to a 450-gram bear brain. And yet our olfactory bulb is the size of a pencil eraser. The bear's is the size of your thumb. That's a lot of smell power for such a small brain.
Bears are thought to have the best sense of smell of any animal on earth. For example, the average dog’s sense of smell is 100 times better than a humans. A blood hound’s is 300 times better. A bear’s sense of smell is 7 times better than a blood hound’s or 2,100 times better than a human.
Broad Patterns of Evolution
In biology and ecology, extinction is the end of an organism or of a group of organisms, normally a species. More than 99 percent of all species, amounting to over five billion species,that ever lived on Earth are estimated to be extinct.
Cryolophosaurus; "CRY-oh-loaf-oh-SAWR-us") is a genus of large theropods known from only a single species Cryolophosaurus ellioti, known from the early Jurassic period of Antarctica
201 - 145 million years ago
The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles.
Past organisms were very different from those presently living, these changes, recorded by fossils illustrate macroevolution. The broad pattern of evolution above the species level.
The Fossil Record Documents Life's History
Large marine reptiles were important predators
Largest known carnivore of its day, was more closely related to mammals than reptiles. The large sail may have played a role in temperature regulation
Some prokaryotes bind thin films of sediments together, producing layered rocks called stromatolites. Sharks Bay, Australia
is the richest source of fossils
- Geology; a single bed of sedimentary rock, generally consisting of one kind of matter representing continuous deposition.
: Fossilized tree sap encasing insects
- Frozen mammals
The fossil record is a remarkable detailed account of biological change over the vast scale of geological time.
As rich and substantial and significant as the fossil record is, it is an incomplete chronicle of evolutionary change. Many organisms just weren't in the right place at the right time.
The gaps in the the fossil record continue to get filled in with each new discovery.
300 - 270 mya
How Rocks and Fossils are Dated
falls under the sub-discipline of geology known as stratigraphy. Stratigraphy is the science of rock strata, or layers. Layering occurs in sedimentary rocks as they accumulate through time, so rock layers hold the key to deciphering the succession of historical events in Earth's past.
It can compare two fossils by position but cannot tell you the actual age.
determining the age of a rock layer and the fossils around it based on the amount of radioactive isotopes remaining within it.
different forms of the same element based on varying numbers of neutrons in the nucleus.
the amount of time necessary for half of a radioactive substance to decay to a stable substance.
Neanderthals - extinct / appearance first modern humans
The Geologic Record
Geologic record: a standard time scale that divides Earth's history into four (4) eons and further subdivisions
Eon: a measure of time in Geology, accounting for about a Billion Years
Hadean - Archaean - Proterozoic
: the first three eons lasted approximately 4 billion years
: roughly the last half-billion years; most of the time that animals have existed on earth
Phanerozoic Eon: divided into (3) eras
Paleozoic: six (6) periods:
Mesozoic: three (3) periods:
Cenozoic: three (3) periods:
Sudden increase in diversity of many animal phyla
Marine algae abundant, colonization of land by fungi, plants, and animals
Diversification of vascular plants, hinge jawed fish
Diversification of bony fish, first tetrapods, insects appear
first four-limbed vertebrates and their descendants, including the living and extinct amphibians, reptiles, mammals, birds, and some extinct fish.
Extensive forests of vascular plants, first seed plants, origin of reptiles, amphibians dominant
Radiation of reptiles, origin of present day insects,
Cone-bearing plants, origin of mammals, dinosaurs evolve and radiate
Gymnosperms are dominant plants, dinosaurs dominate, abundant, and diverse
Flowering plants appear, many groups of organisms, including most dinosaurs become extinct at end of period
Radiation of mammals, birds, and pollinating insects - early, Origins of many primate groups - late
Earliest direct human ancestors, continued radiation of mammals and angiosperms - early; Appearance of bipedal human ancestors
Ice age, origin of genus Homo - early
Historical time - present
The Rise and Fall of Groups of Organisms
Anerobic prokaryotic organisms flourshied and then declined as the oxygen content of the atmosphere rose.
Billions of years later tetrapods emerged from the sea giving rise to several new groups of organisms.
Amphibians went on to dominate life on land for 100 million years until dinosaurs and mammals became dominant.
The rise or fall of any particular group of organisms is related to the speciation and extinction rates of its member species
The theory of plate tectonics: the continents are part of great plates of Earth's crust that essentially float on the hot, underlying portion of the mantle.
Movement in the mantle causes the plates to move over time in a process called continental drift.
One spectacular example of this theory occurred 45 million years ago when the Indian plate crashed into the Eurasian plate, giving rise to the formation of the Himalayan mountains.
The fossil record shows that the majority of species that have ever lived on Earth, have already gone extinct.
Although extinction occurs on a regular basis, at certain times disruptive changes to the global environment have caused the rate of extinction to dramatically increase.
The "Big Five" Mass Extinction Events
Fossil records indicates that the diversity of life has increased over the past 250 million years, which was fueled by adaptive radiations.
Adaptive radiations is evolutionary changes in which groups of organisms form many new species, whose adaptations allow them to fill different ecological roles, or niches, in their communities.
Adaptive radiation has occurred after each of the five major extinctions.
Adaptive radiation has also occurred in groups of organisms that possessed major evolutionary innovations, such as seeds, armored body coverings, or that they colonized regions in which there is little competition from other species
The Cambrian Explosion
Why The Explosion?
Increasing mineral availability
Bilateral symmetry: evolutionary innovation
Nerve and sense organs
Front gut opening - anus at other end
Increased rate of evolution
Or was it - Recovery from Mass Extinction
Eons - Eras - Periods