Evidence of Evolution & Early Theories PDF

EVIDENCE OF EVOLUTION & EARLY THEORIES Hypothesis and Theories p 188  THEORY OF EVOLUTION Theory of evolution has been developed over many years by many different scientists. Evolution is regarded as a scientific theory since various hypotheses relating to evolution have been...

EVIDENCE OF EVOLUTION & EARLY THEORIES Hypothesis and Theories p 188  THEORY OF EVOLUTION Theory of evolution has been developed over many years by many different scientists. Evolution is regarded as a scientific theory since various hypotheses relating to evolution have been tested and verified over time. THEORY VS HYPOTHESIS A theory is an explanation of something that has been observed in nature which can be supported by facts, generalisations, tested hypotheses, models and laws. A hypothesis is a possible solution to a problem. WHAT IS EVOLUTION?  EVOLUTION Evolution means change over time. It is the process by which organisms develop over time from earlier forms. Biological evolution – refers to any genetic change in a population that is inherited and becomes a characteristic of that population over several generations. * Life forms descended from/related to organisms in the past. became modified from one generation to a next. Biological evolution in harmony with changes of earth  Things we see today arose from things that already existed in the past but look different because things change over time Variation in offspring p 190  POPULATION & SPECIES Species: a group of organisms – that have a large number of similar characteristics – are able to interbreed Population: – organisms of the same species – occupying the same habitat at the same time, – and having the ability to interbreed. Variation refers to small differences that exist between individuals of a species or population – height, differences in eye colour  Similarities Genetic evidence that organisms are closely related and are likely to have a common ancestor includes: Identical DNA structure Similar sequence of genes Similar portions of DNA with no functions Similar mutations (mt DNA) Species that are closely related have greater similarity to each other.  SOURCES OF VARIATION 1. Crossing- over 2. Random arrangement of chromosomes during meiosis 3. Random fertilization of gamete 4. Mutations Mutation: It involves a change to structure of a gene. This leads to an altered genotype resulting in a different or altered phenotype. Crossing over: During prophase 1 there is an exchange of chromatid segments between homologous chromosomes. When meiosis is complete, new combinations of genetic material results in gametes, making them different from each other. Mutations  Oorkruising/Crossing over Slegs in meiose In meiosis only Profase/Prophase I Random arrangement of chromosome: Chromosomes arrange randomly at equator during metaphase 1 and 2. As result, during anaphase 1 and 2, the chromosomes or chromatids may move to poles in different combinations. Leading to gametes that differ from each other. Random fertilisation of gametes: Ovums and sperm cells produced by meiosis are different from each other. There is random fertilisation of these gametes, there will be different combinations in offspring.  Random arrangement of homologous pairs on equator. Random Fertilization Continuous variation and Discontinuous variation  1. Continuous variation Different phenotypes for the same characteristic There ia a range of measurements in a population. Height of learners in class – complete range of heights eg 1,5m – 1,65m. Shoe size, Milk yield in cows and width of hand span Results from combined effect of several genes in an organism – polygenic inheritance Is also affected by the environment. – height of a human is genetically determined – influenced by environmental = diet.  If you plotted a graph - bell shaped curve  2. Discontinuous variation Individuals in a population can be put into groups or categories. Groups based on characteristics that cannot be measured across a range. Either has the characteristic or it does not have it - there are no in-betweens Eye colour and blood groups in humans. Controlled by alleles of a single gene or small number of genes. Environment does not affect it.  FIELDS AS EVIDENCE FOR THE THEORY OF EVOLUTION 1. Paleontology 2. Comparative (Vergelykende) anatomy 3. Biogeography 4. Molecular biology and genetics 5. Comparative embryology Scientist’s major assumption (veronderstelling): – Species change through natural selection Evidence is presented to show that different species are related – they have common ancestors.  Paleontology Study fossils History of extincted organisms  1. Evidence from Paleontology = study of fossils Fossils = remains of ancient life forms preserved in: – rocks, – ice, – tar – the dried sap of trees = amber Scientists try to tell age of a fossil: – relative dating = how it is related to the age of another fossil -geological event – Only tell us whether a fossil was formed – before or after another fossil or before or after a geological event. Relative dating  Radiometric dating - attempts to find out how long ago a fossil was formed. Radiometric dating  Scientists have interpreted the fossils record to mean that: The Earth is about 4.5 billion years old First life forms (the Prokaryotes) developed on Earth about 3.8 billion years ago - existed in the oldest rock forms life forms in existence today are more complex – they occur in more recent rocks Today's life forms are different from the fossils: – fossils of the first horses were small as foxes Many life forms are extinct. Archioptrix  2. Evidence from Comparative Anatomy The forelimbs of (mammals) – moles, – bats, – horses, have different functions – seals and all built on the same basic plan – monkeys They all have: – one large bone attached to two smaller bones, – attached to several small bones, – attached to approximately 5- digits  Charles Darwin interpretation of the structural differences 1. The forelimbs of all mammals arose from that of a common ancestor 2. The forelimbs had the same basic plan. 3. These structures now show variations (differences) because they became modified to perform different functions. Refer as divergent evolution = formation of new species from a common antcestor. * The basic plan, would differ if these structures developed independently in each animal.  HOMOLOGOUS STRUCTURES = Structures in different species – are similar to each other – because they come from a common ancestor All the species with homologous structures – have arisen from a common ancestor – they became adapted to live in different environments. = Adaptive radiation – usually occurs when environmental changes HOMOLOGOUS STRUCTURES Adaptive radiation from a common ancestor  3. EVIDENCE FROM BIOGEOGRAPHY = the study of past and present distribution of individual species. 1. that closely related species tend to be found in the same geographic region 2. very similar habitats (the same ecological niches) in distant regions are occupied by very different species Island species resemble their respective mainland species  Convergent evolution Two similar ecological niches in different parts of the world may show some similarities. Darwin explained : – that these similar structures have evolved independently – from different ancestors. – =convergent evolution. – Similar structures that have come about by convergent evolution from different ancestors are called analogous structures. (a nelle gis) Convergent evolution  4 Evidence from Molecular Biology and Genetics Does not try to show that organisms changed from one to the other It tries to show that they are related. Evidence comes from: 1. DNA structure - has not changed in 3 billion years 2. The sequence of genes and proteins - 46% of yeast genes and 61% of the genes of the fruit fly = in similar sequence to those of humans. Closer similarity,more closely related 3. Identical protein synthesis - exactly the same in all living organisms. 4. Similar metabolic pathways. - aerobic respiration, all do it through Krebs Cycle and the Electron Transport System. 5. Evidence from Comparative Embryology = Study of similarities and differences in the way organisms develop. Examine patterns: – from the early stages of development (embryo) – to the fully grown organism. Embryos of mammals, birds, lizards and snakes look like each other in early stages Embryos of dogs and humans have slits in their neck regions corresponding to the gill slits of a fish  THEORY OF RECAPITULATION the embryo of an organism (during its development) passes through the adult stages of all its ancestors »Homework p 196 »END OF SLIDES. 3. Homologous structures show a similar pattern of structures√, – because they arose from a common ancestor√ – by adaptive radiation√ to different environments. Analogous structures may show similarities in structure and/or function√ – but they evolved independently √ – from different ancestors by convergent evolution√ (6). 4. the Earth is about 4.5 billion years old √ the first life forms (the Prokaryotes) developed on Earth about 3.8 billion years ago and they existed in the oldest rock forms√ life forms in existence today are more complex √ than any of those that lived in the past, and they occur in more recent rocks  most of today's life forms are different from the fossils of ancient life√ many of the life forms that existed in the past are no longer in existence today; they have become extinct √ (5)  5. identical DNA structure√ similar sequence of genes and proteins√ identical protein synthesis√ similar metabolic pathways√ (4) /21/  EXTINCTION = death of all members of a particular species They have been occurring constantly at a low rate usually matching the rate at which new species occur. Mass extinctions - more than 50% of the Earth's species vanish in a few million years. At least five major extinction events. Vredefort crater RSA Bigest in the globe! Volcano’s in RSA Vredefort crater RSA Bigest in the globe!  Vredefort The asteroid to hit Vredefort, South Africa, is one of the largest ever known to have hit the Earth; estimated at over 10 km (6 miles) wide. At slightly over 2 billion years old, the Vredefort Crater is one of the few existing multi-ringed craters on Earth (they are usually erased by geological activity).  VREDEFORT DOME WORLD HERITAGE SITE - FREE STATE - SOUTH AFRICA meteorite larger than Table Mountain slammed into the ground near what is now Vredefort in the Free State. The resulting thousand-megaton blast of energy was nature's equivalent of a nuclear catastrophe. Except that in this case, life was probably kick- started by the development of oxygen and multicellular life linked to the impact. WHAT IS EVOLUTION? P.305  WHAT IS EVOLUTION? P.305 Theory :all the things we see today arose from things that existed in the past They look different - change over long periods of time. Biological evolution: – changes that living things have undergone – Over long periods of time (Inductive) All present-day life forms – descended from, – and are related to, those that lived in the past (deductive) – Present-day life forms may look different – They became modified from one generation to another. Theory of evolution also referred to as the theory of "descent with modification". Sometimes, the modifications are so great that it is difficult to see the connection (the similarities) between the modern form and its ancestor.??????? Carbon Dating.  GRAWE (MOL) DIGGING (MOLE) VLIEG (VLERMUIS) FLYING (BAT) BASIESE LIGGAAMSPLAN EVOLUSIE HARDLOOP (PERD) RUNNING (HORSE) BASIC BODY EVOLUTION PLAN SWEM (DOLFYN) SWIMMING Common Modification of body plan (DOLPHIN) Ancestor for a specific mode of life KLIM (AAP) CLIMBING (APE) analogous structures.  Facts, Generalisations, Hypothesis, Models, Laws and Theories Scientists built up knowledge trying to explain things observed in nature. 'inquiry‘(ondersoek) = a search for information and explanation. discovering and describing -------explaining nature Observations are made, data or facts are collected and recorded………. carefully analysed. Then scientists come up with generalisations  INDUCTIVE REASONING. Inductive reasoning = the process of arriving at a generalisation based on large number of observations 'all living organisms are made up of cells'.?????? (Schleiden & Schwann)  DEDUCTIVE REASONING Scientists have ‘possible explanations’ for their observations = hypotheses Hypothesis testing = designing and carrying out the investigation to test the hypothesis. = During hypothesis testing, the generalisation is used to predict a specific result. Generalisations : 1. all living organism are made up of cells Prediction: that humans are made up of cells.  MODELS: Scientists often use (physical and mathematical) to explain their generalisations and hypotheses. – the double-helix model of DNA. LAWS ( Larger Generalisations) Scientists may use: – facts, – generalisations, – tested hypotheses and – models to come up with laws e.g. the law of gravity.  What we already know about Diversity of life and Evolution (Gr 10 &11) Biodiversity = The wide range of species and the number of organisms making up each species – microscopic organisms ------ very large plants and animals The five kingdom classification: – Monera, – Protista, – Fungi, attempted to show evolutionary relationships – Plantae and – Animalia).  INFORMATION FROM FOSSILS AND BIOGEOGRAPHY AS EVIDENCE FOR EVOLUTION. Evolution of the major taxa took extremely long periods of time. The Geological Time Scale. Explained how life itself began by means of the Oparin- Haldane Hypothesis. Earth began as a huge ball of fire ± 4-6 billion years ago. cooled, gases released : hydrogen, methane, ammonia…. oxygen present??????, Ultraviolet light and lightning – changed these gases into organic molecules – proteins and fatty acids='building block's of life. The fatty acids + proteins =cell membranes. Formation of cells??? Scientist's interpretation of fossils, cells existed from about 3.4 billion years ago.. Simplest life forms on Earth ± 4 billion years ago = during pre-Cambrian times Cambrian period (543 - 505million) – major groups of animals appeared Porifera, Coelenterata, Platyhelminthes, Nematoda. GR 10 Annelida, Mollusca, Arhropoda, Echinodermata and Chordata).  Based on their interpretation of the fossil records: – fishes, – amphibians, – reptiles, end of the Cambrian Period – birds, 505 million years ago – mammals (humans) Extinctions natural events – 5 major extinctions.