Presentation on theme: "Origin of Life PANSPERMIA A comet or meteorite brought micro-organisms."— Presentation transcript:
Origin of Life
PANSPERMIA A comet or meteorite brought micro-organisms
TIDAL POOLS UV light / electrical discharges through volcanic gases onto water
UNDERSEA THERMAL VENTS Gases, energy and catalysts (metal sulphides)
Theories of Origins of Life EVIDENCE (cant do experiments!) Fossils, biochemical links, DNA testing 3 MAIN THEORIES: Panspermia, Thermal vents, Tidal pools, lightning & volcanoes REQUIREMENTS: water, energy (heat / lightning), inorganic mol.s or gases Panspermia theorists dont believe the correct conditions were available at the time that life arose on Earth All agree that basic nucleotides, were vital in order to reproduce organic molecules
Scientists have been able to manufacture organic molecules in the laboratory in the presence of water, heat and gases.
Chloroplasts and mitochondria both have nucleic material. They may have been separate organisms which were incorporated into cells
Genetic variation MEIOTIC MUTATIONS source of all variation – gamete genes are different SEXUAL REPRODUCTION increases variation – different combinations of genes in gametes 1. cross-over and recombination 2. independent assortment of chromosomes 3. fertilisation - fusion of random gametes
Gene Pools Species may be divided into populations or demes by geographical obstacles Population - group of individuals of the same species which can interbreed Gene pool is the total group of genes available for reproduction in a population
Gene flow – movement of genes from one population to another via gametes Deme – local unit of a population Genetic equilibrium – allele frequencies of a population remain unchanged from generation to generation (Hardy-Weinberg)
Geographical barriers isolate gene pools and prevent normal gene flow between demes mountains glaciers sea rivers POPULATION 1 POPULATION 2
Hardy-Weinberg Theorem Allele frequencies in a population remain constant - from generation to generation unless disturbed. Hardy–Weinberg equilibrium is impossible in nature Ideal state baseline to measure genetic change against. non-random mating, mutations, selection, limited population size, "overlapping generations", random genetic drift, gene flow and meiotic drive.
Gene pool stability Large population Random mating No gene flow No mutations No Natural selection Small population Assortative mating Gene flow (migration) Mutations Natural selection Gene pool change Hardy Weinberg theory true Not true - microevolution