Humans used to be pongidae (apes) long time ago. This data is found by fossil records. In 1925, A kull which was the first to be classified as Australopithecus. It looked like ape in appearance, but had human-like teeth. As the amount of finds increased, so did the number of species. Australopithecus are small-brained gracile hominids with mixed fruit/vegetable diet. Paranthropus, smalled-brained robust hominids with a grassland vegetable diet. Homo, large-brained hominids with an omnivorous diet. These are brief descriptions of the evolution. After homo, human now have started living.
WHAT IS "ORIGIN OF SPECIES"?
A work published by Charles Darwin. Darwin introduced the concept of natural selection. Suppose a member of a species were to develop a functional advantage, such as a reptile grew wings and learned to fly. Its offspring would inherit that advantage and pass it on to future offspring. Naatural selection would act to preserve the advantageous trait. Essentially, natural selection is the naturalistic equivalent to domestic breeding. Over the centuries, human breeders have produced dramatic changes within domestic animal populations simply by selecting individuals to breed. They have been able to accentuate desirable traits and even suppress undesirable traits gradually over time. The different between domestic breeding and natural selection is: rather than human breeders making the selections, nature itself is the selector/
WHAT IS EVOLUTION, EXACTLY?
Biological evolution is change in the properties of populations of organisms or groups of such populations, over the course of generations. The development, or ontogeny, of an individual organism is not considered evolution: individual organisms do not evolve. The changes in populations that are considered evolutionary are those that are ‘heritable' via the genetic material from one generation to the next. Biological evolution may be slight or substantial; it embraces everything from slight changes in the proportions of different forms of a gene within a population, such as the alleles that determine the different human blood types, to the alterations that led from the earliest organisms to dinosaurs, bees, snapdragons, and humans.
SUMMARY:
There are four types of adaptations: behavioral adaptations, structural adaptations, biochemical adaptations, and physiological adaptations. The primary mechanism of evolutionary change producing adaptation of organisms to their environment is natural selection. In the century prior to Darwin, the study of fossils suggested that species had changed over time. Use and disuse, and inheritance of acquired characteristics are mechanisms of evolution of life on Earth. Because of Lyell's Principles of Geology, Darwin came to realize that the organisms on Earth changes over time. He observed that organisms produce more offspring than the environment can support, and organisms vary in many traits. Darwin found convincing evidence for his ideas in the results of artificial selection, the selective breeding of domesticated plants and animals.
- Individuals do not evolve: populations evolve
- Natural selection can amplify or diminish only heritable traits; acquired characteristics cannot be passed on to offspring
- Evolution is not goal directed and does not lead to perfection; favorable traits vary as environments change
This is an example of evolution. This is how organisms keep evolving to be better depending on environment. Initial use of pesticides favors those few insects that have genes for pesticide resistance. With continued use of pesticides, resistant insects flourish and vulnerable insects die. Proportion of resistant insects increases over time.
The fossil record shows that organisms have evolved in a historical sequence. We are able to tell how old they are by layers of rock, or sand. Homologous structures and genes can be used to determine the branching sequence of an evolutionary tree. Populations may be isolated from one another, or individuals within populations may interbreed. Mutation is the ultimate source of new alleles. Occasionally, mutant alleles improve the adaptation of an individual to its environment and increase its survival and reproductive success. Sexual reproduction shuffles alleles to produce new combinations because it crosses over the chromosomes. However, sexual reproduction alone does not lead to evolutionary change in a population. Although alleles are shuffled, the frequency of alleles and genotypes in the population does not change. Hardy Weinberg principle states that allele and genotype frequencies within a sexually reproduction, diploid population will remain in equilibrium unless outside forces act to change those frequencies. If a population is in Hardy-Weinberg equilibrium, allele and genotype frequencies will not change unless something acts to change the gene pool. For a population to remain in Hardy-Weinberg equilibrium for a specific trait, it must satisfy five conditions: Very large population. No gene flow between populations. No mutations. Random mating. No natural selection. If those five conditions are not met in a population, the population's gene pool may change. The three causes of evolutionary change: Natural selection, genetic drift, and gene flow. Stabilizing selection favors intermediate phenotypes, acting against extreme phenotypes. It is very common, especially when environments are stable. The evolution of antibiotic resistance in bacteria is a serious public health concern. Diploidy and balancing selection preserve genetic variation. Natural selection is not able to fashion perfect organisms. It can only act on existing variation, and evolution is limited by historical constraints. Adaptions are often compromises. Also chance, natural selection and the environment interact.
This is a diagram of archaeopteryx fossil. Feathers were one of the first and the most successful structures that birds evolved. It is believed the feathers first evolved from reptile scales as an adaptation to permit endothermy. As endothermic organisms, birds maintain a constant body temperature. The insulation provided by the feathers greatly reduces the amount of energy required to keep up the body heat. Without this insulation, the birds would be forced to eat impossible amounts of food, and undergo cellular respiration to produce heat.
http://www.youtube.com/watch?v=zVEjVIo-jro
This video also talks about the evolution of birds from dinosaurs.
KEY TERMS:
- Biogeography: the geographic distribution of species, suggested to Darwin that organisms evolve from common ancestors
- Comparative Anatomy: the comparison of body structures in different species
- Homology: the similarity in characteristics that result from common ancestry
- Comparative Embryology: the comparison of early stages of development among different organisms
- Molecular Biology: comparisons of DNA and amino acid sequences between different organisms reveal evolutionary relationships
- Evolution: the change in heritable traits in a population over generations
- Gene Pool: the total collection of genes in a population at any one time
- Microevolution: a change in the relative frequencies of alleles in a gene pool over time
- Population Genetics: the study of how populations change genetically over time
- Modern Synthesis: connection between Darwin's theory and population genetics
5 FACTS:
1) Darwin was the first to represent the history of life as a tree.
2) Fossil record tells how old it is, and it can lead how the organism evolved.
3) There are about 8 million combinations possible in a human sperm or egg due to independent assortment during meiosis.
4) p2 + 2pq + q2 = 1 (homozygous dominant + heterozygous + homozygous recessive = 100%)
5) The Hardy-Weinberg equation can be used to test whether a population is evolving.
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