Evolution • the process of cumulative change in the heritable characteristics of a population
Players in Evolution • Jean Baptiste de Lamarck (1744-1829) • Russel Wallace (1823-1913) and Charles Darwin (1809-1882)
Natural Selection • A process in nature in which organisms possessing certain genotypic characteristics that make them better adjusted to an environment tend to survive, reproduce, increase in number or frequency, and therefore, are able to transmit and perpetuate their essential genotypic qualities to succeeding generations.
Evidence for Natural Selection • Fossil Records • Artificial Selection • Homologous Structures
Mechanisms of Evolution • Too many offspring • over production of offspring leads to intra-species competition and survival of the individuals best suited to that particular environment. • competition can also lead to adaptive behaviours. • Natural Variation in a Population • random assortment of chromosomes • crossing over of segments of chromosomes result in new combinations of genes, different than the parental combinations • random fusion of gametes in sexual reproduction • additional variations arise due to mutations, either chromosomal or gene
Natural Selection Summarized • The favourable characteristics are expressed in the phenotypes of some of the offspring • These offspring may be better able to survive and reproduce in a particular environment; others will be less able to compete successfully to survive and reproduce. • Examples • Antibiotic Resistant Bacteria • Peppered Moth • Heavy Metal Tolerance in Plants
Introduction • Biologists believe that organic evolution by natural selection accounts for the major steps in evolution. • macroevolution – major developments such as the origin of the eukaryotic cell, the origin of multicellular organisms, and the origin of vertebrates from non-vertebrates • microevolution – the relatively minorchanges that arise and lead to the appearance of new, but closely related species. • Theory of evolution - the Big Bang.
Four Processes for the Spontaneous Origin of Life • Chemical Reactions to produce simple organic molecules, from inorganic molecules • Assembly of the molecules into polymers • Self Replication of Polymers • Development of Membranes to enclose the polymer
Chemical Reactions to Produce Simple Organic Molecules • Heat, Temperature and Lightning – Miller and Urey Experiment • Recreated ancient atmosphere (nitrogen, water vapour and carbon dioxide, smaller amounts of methane, ammonia, carbon monoxide, sulphur dioxide, hydrogen sulphide and hydrogen cyanide. • Lightning and UV radiation to provide energy
Chemical Reactions to Produce Simple Organic Molecules • Other Possibilities • In Space – Panspermia • Alternating Wet and Dry Environments • Near Volcanos • Deep Sea and Ocean Vents
Formation of Polymers and Self-replication - RNA • As the organic compounds are made, they arrange themselves in lines – polymers (Using the Clay Lattice as a template) • Lines of molecules form early enzymes (ribozymes) • Catalyse reactions, such as peptide bond formation • RNA strand is made and due to enzymes, a complementary strand can be made, and then copies are made • Longer and longer double stranded pieces are made, forming , now DNA • DNA more useful as it is longer and can hold more information (RNA – 1500 nucleotides max)
Development of Membranes - Protobionts • Membranes were needed to separate the external environment from the internal environment • Phospholipids would have formed and due to hydophilic and hydrophobic properties, would form spheres in water (called coacervate) • Due to the bilayers, an internal environment would form, and if the early molecules (RNA to DNA) were trapped in the membrane, protobionts would have formed
Prokaryotes and the Oxygen on the Atmosphere • Early cells were anaerobic and heterotrophs • As nutrients decreased in amount, some evolved to become chemoautotrophic, using the gases in the air • Since there was a large amount of CO2, some early prokaryotes used the gas, to produce early carbohydrate. The waste product was O2, which went into the atmosphere
Prokaryotes and the Oxygen on the Atmosphere (continued) • The formation of an ozone layer in the upper atmosphere commenced • The ozone layer began to reduce the incidence of UV light reaching the Earth’s surface. • Terrestrial existence (rather than life restricted to below the water surface) became a possibility • Other prokaryotes, simply ‘fed’ on the organic molecules available in their environment. • The bacteria had evolved aerobic respiration and so had the enzymes not only of glycolysis, but also of the Krebs cycle and terminal oxidation.
Definitions – Neo - Darwinism • Gene Pool – all of the genetic information present in the reproducing members of a population at a given time • Allele Frequency – is a measure of the proportion of a specific variation of a gene in a population. • The allele frequency is expressed as a proportion or a percent, and can be calculated by the Hardy-Weinberg equation (more later). • For example, it is possible that a certain allele if present in 25% of the chromosomes studied in a population. One quarter of the loci for that gene are occupied by that allele. Keep in mind it is not the same as the number of people who show a particular trait.
Species and Speciation • Species • Morphological Definition • A type of organism that has fixed characteristics that distinguish it from all other species • Biological Definition • Group of actually or potentially interbreeding populations, with a common gene pool, which are reproductively isolated from other such groups
Species and Speciation • Speciation • the evolution of new species, requires that allele frequencies change with time in populations. • Mechanisms = Isolation • Geographic (Allopatric) • Temporal (Sympatric) • Behavioral (Sympatric)
Species and Speciation (Animation) • Geographical Isolation (Allopatric) • Ex. Galapagos Islands • Ex. Snails • Lizards
Species and Speciation • Temporal (Sympatric) • Ex. Plants and Apple Maggot Fly • Behavioral (Sympatric) • Ex. Konrad Lorenz and the Gwan • Movie • Hybrid Infertility
Species and Speciation – Trends in Evolution • Adaptive Radiation • many similar but distinctive species evolve relatively rapidly from a single species or from a small number of species.
Species and Speciation – Trends in Evolution • When the species evolves different ways, this is called DIVERGENT EVOLUTION • Thenew species is different than the first, in terms of the adaptations that have taken place
Species and Speciation – Trends in Evolution • Living organisms often find the same solution to particular physiological problems, and as a result the organisms, in response to their environment, can become morphologically similar, even though they are not related to a common ancestor. • This is called CONVERGENT EVOLUTION
Species and Speciation – Rates of Evolution • Gradualism • Punctuated Equilibrium
Species and Speciation • Transient Polymorphisms • When there are two alleles for a gene in the gene pool, it is called polymorphic. • If one allele is gradually replacing the other, based upon environmental pressures, this is called balanced polymorphism • Ex. Peppered Moth (Biston betularia)
Species and Speciation • Balanced Polymorphism • When two alleles of a gene can persist indefinitely in the gene pool of a population • Ex. Sickle Cell Anemia • HbN HbN – normal • Hbn Hbn - Sickle Cell anemic but immune to malaria • HbN Hbn – heterozygous, slight anemia, but resistant to malaria
Human Evolution • Humans are known as Homo sapiens (modern man). The full classification is: • Kingdom: Animalia • Phylum: Chordata • Subphylum: Vertebrata • Class: Mammalia • Subclass: Eutheria • Order: Primates • Suborder: Anthropoids • Family: Hominidae • Genus: Homo • Species: Sapiens
Human Evolution • Use Fossil Records as evidence • Use Carbon – 14 Dating to see how old the fossil or artefact is. • For C14, the half-life is 5730 years. • For fossils and rocks older than 60 000 years, we use K40 dating.
Human Evolution – Humans as Primates • What defines humans as primates? • Opposable Thumbs for grasping • Mobile arms with shoulder joints allowing movement in three planes and the bones of the shoulder allowing force to be applied to the arms. • Stereoscopic vision • Skull Modified for upright posture – Magnum foramen
Trends in Hominid Fossils • Ardipithecus ramidus • Lived approximately 5.8 – 4.4 mya in Ethiopia
Trends in Hominid Fossils • Australopithecines • A. afarensis from the Afar desert (4-2.8 mya) • A. africanus (3-2 mya) found in South Africa. • A. robustus (2-1.4 mya) in South Africa.
Trends in Hominid Fossils • A. Africanus
Trends in Hominid Fossils • Homo genus. • They were from around 2 mya and had larger brains (600 cm3) and walked upright. • H. habilis (handy man). thought he arose from A. afarensis 2 mya in East Africa and used simple tools. • Homo erectus was from Africa. It is thought it migrated to other parts of the world and had a larger brain than H. habilis. • H. neanderthalensis, which lived in Eurasia from 200 000 to 30 000 years ago • Next was H. sapiens, which came to Europe.
Trends in Hominid Fossils • H. Habilis
Trends in Hominid Fossils • H. Erectus
Trends in Hominid Fossils • H. Neadrathalis
Trends in Hominid Development • Hominid Diets and Brain Size • Australopithecus brains were only slightly larger in relation to body size than the brains of apes. • Powerful jaws meant a largely vegetarian diet. • 2.5 mya, Africa became drier, led to an evolution for survival, as there were less plants • Tools to hunt, increased supply of protein correspond to the changes in brain size
Trends in Hominid Development • Hominid Diets and Brain Size • The correlation between the change in diet and the increases in brain size can be explained in two ways • 1. Eating meat increases the supply of protein, fat and energy in the diet, making it possible for the growth of larger brains • 2. Catching and killing prey on the savannas is more difficult than gathering plant foods, so natural selection will have favoured hominids with larger brains and greater intelligence.
Trends in Hominid Development • Genetic and Cultural Evolution • In the recent evolution of humans, cultural evolution has been very important and has been responsible for most of the changes in the lives of humans over the last few thousand years. • This is much too short a period for genetic evolution to cause much change. • Some aspects of cultural evolution, ex. Medicine, have reduced natural selection between different genetic types and therefore, genetic evolution.
Classification and the Binomial System • Classification • The process of classification involves giving every organism an agreed name and arranging organisms into groupings of apparently related organisms. • Scheme of the overall diversity of living things. • Classification attempts to reflect evolutionary links.
Classification and the Binomial System • The Binomial System • Carolus Linnaeus in the 18th Century • The first part of the name is the genus or the generic name based upon a noun. • The second name is the species, or the specific name, based upon an adjective. • Ex. Canislupis – dog / wolf and grey /brindled coat
Classification and the Binomial System • Scheme of Classification • Kingdom – largest and most inclusive grouping • Phylum / division – organisms constructed on a similar plan • Class – a grouping of orders within a phylum • Order – a group of apparently related families • Family- a group of apparently related genera • Genus - a group of similar and closely related species • Species – a group of organisms capable of interbreeding to produce fertile offspring