Features of the History of Life on Earth PDF

Features of the History of Life on Earth The geological time scale is used by scientists in order to divide the history of life on earth with each time period. This serves as a calendar of events which shows major climatic and geological events. This also shows the events t...

Features of the History of Life on Earth The geological time scale is used by scientists in order to divide the history of life on earth with each time period. This serves as a calendar of events which shows major climatic and geological events. This also shows the events that greatly affect the disappearance and emergence of species overtime. Try to look and memorize these units in order for you to understand the geologic timescale. - EON- unit of time equal to a billion years - ERA- division of time in an eon without a fixed number of years. - PERIOD- subdivision of era which the length is based on the fossil evidences - EPOCH- time wherein a memorable event occur  Below is an example of a comprehensive timescale of each ere with its important events and organisms’ characteristics (Siyavula: Technology Powered Learning, n.d. ). IMPORTANT EVENTS CHARACTERISTIC OF ORGANISMS PRE- HADEAN: - Prokaryotes evolved which can photosynthesize CAM (cyanobacteria). It releases oxygen and lives in water. - Earth’s crust cooled BRIA - Stromatolites are formed. These are colonies of bacteria N - Oceans and atmosphere began to form built from minerals and sediments layer upon layer. - various chemical reactions occurred - First soft bodied animal came to life known as 4.5 Swartpunia. billio ARCHEAN: n years - unicellular organisms emerge -atmosphere is entirely made of volcanic ashes PROTEROZOIC- earliest form of sexual reproduction allowing an increase of diversity of organisms -Forest with primitive plants covered the - First fish (chordates) appeared which mammals Earth’s surface increasing oxygen. descended from. Later on, fishes developed spiny bones and jaws with teeth. - Amphibian became diverse and moved in land - Animals with exoskeleton (trilobites) became diverse PALE OZOI -Reptiles colonized land -First insect appeared and developed wings later on C 542 -Gymnosperms replaced earlier plants TI 251 millio n years - Age of reptiles in marine and terrestrial - Dinosaurs appeared on land MES habitats - Flying reptile (Pterosaurs) conquered the sky and OZOI - Climate changed from cooling to ichthyosaurs dominated the oceans C warming periods. - Archaeopteryx evolve- combination of bird and reptile 251- - Pangea existed 72 - Extinction of species in Paleozoic era led millio to rapid evolution of life forms n - Dinosaurs became extinct during the years Cretaceous period.  - Gymnosperms dominated the land -Age of mammals - Grass species evolved - Animals fit to open landscape allowing the predator-prey -Pangea drifted dividing it into continents relationship CEN - Africa was an island not joined by - Homo sapiens started to evolve OZOI Europe and Middle East C - 55 million years, the climate is warmed 65 but became cool on its 49th million year millio - Grasslands expanded and forests shrank n years Mechanisms that Produce Change in Populations Research Populations always evolve. Evolution means that there is a change in genetic makeup of each population over generations. If a population is placed in a steady condition, with no changes in genetic makeup, the principle is called HARDY- WEINBERG EQUILIBRIUM. However, there will always be a change in evolution, thus the principle is not followed. Allele is the variant form of gene. Let’s make it into a concrete example. Imagine that you have a large population of butterflies. The butterflies’ population come into its wings colour, and their colour is identified by a X gene. Xx and XX butterflies are red and xx are blue. In our assumed population, X allele has a frequency 0f 0.30 while x allele has a frequency of 0.70. If it is in a Hardy Weinberg equilibrium, allele frequencies will be related to its genotype frequencies by a mathematical relationship. p^22squared + 2pq + q^2 = 12=1squared, equals, 1 p = frequency of X, q = frequency of x Frequency of XX = p^22squared = 0.7^2 squared = 0.49 Frequency of Xx = 2pq = 2 (0.7) (0.3) = 0.42 It simply showed that the allele in the gamete pool is just the same from one generation to another. If Hardy Weinberg principle is violated, these will come into a different mechanism in evolution. Try to look at the examples below. Mutation is the change in DNA sequence of a gene. It can change from one allele to another but has a small effect on evolution unless it interacts with other factors. Mutation is a source of genetic variation in a population. There are harmful and beneficial contributions of mutation whether it helps an organism to reproduce and mature or not. Example: Mutation can cause the parents’ genes for bright green colour to have offspring with a gene for brown colour (Understanding Evolution, 2020). Natural selection is wherein one allele makes an organism less or more fit in an environment to reproduce and survive. If an allele reduces its fitness, the frequency of its next-generation will tend to drop. For example, tree frogs are commonly eaten by birds and snakes. Green Tree Frogs live in a green vegetation environment in swamps and marshes while Gray Tree Frogs live in dark wooded areas. Green Tree Frogs can be easily detected by a predator if it lives in tree barks. Instead, natural selection favored Tree Frogs to go to habitats that they can be able to camouflage and cannot be eaten by predators (Whittaker, D., 2012). Artificial selection or selective breeding allows humans to choose desirable traits for a plant or animal rather than leaving the species to change and evolve gradually without human interference. For example, a purebred German Shepherd is mated with a purebred Husky. The offspring probably will be a crossbreed half husky, half German Shepherd (Khan Academy, n.d). Genetic drift is the change of allele frequencies in a population by a generation that occurs due to chance events. This is because of sampling error in selecting the alleles for the next generation originated from the gene pool of the current generation. It tends to happen in small populations. For example, a bird may have an allele on two different kinds of beak sizes. Depending on which alleles dominate the offspring, genetic drift can allow one beak size to disappear from a population affecting the genetic variation of the birds' gene pool (Softschool.com). Recombination is the reassortment of genes into a new combination of chromosomes. This occurs in an exchange of DNA between crossing over in meiosis. DID YOU KNOW? Some speculate that during his travels Darwin may have contracted a parasitic illness called Chagas disease that can eventually result in cardiac damage, which ultimately caused Darwin’s death.