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Evolution Year 10 Semester 2 Introduction 1. How old is the universe? About 15 billion years since Big Bang. 2. How old is the Earth? About 4.5 billion years. 3. How long has there been life on the Earth? About 3.5 - 4 billion years 4. When did the separation of man and ape from a common unnamed ancestor occur? Between 5 and 10 million years ago. Introduction 5. How old is the human species (Homo sapiens)? 100,000 to 200,000 years old. 6. Evolutionary theory teaches that humans evolved from monkeys. True or False? False - humans and modern monkeys had a common ancestor. 7. Pope John Paul II does not approve of the theory of evolution. True or False? False, according to book Voices for Evolution. 8. Major Protestant Churches have no problem with the theory of evolution. True or False? True, according to Voices for Evolution. What do you notice about living things? Describe each of the environments in each era. Common Idea…… • Life, both plants and animals, have changed over time to meet the conditions of the environments they live in. Adaptations • Three main types: – Physiological: ? – Structural: ? – Behavioural: ? • An adaptation is a characteristic of a living thing which allows it to survive in the conditions provided by its environment. Evolution • The modern day theory of evolution states that all living organisms share a common origin dating back more than 4 billion years. • Over this period, new species have arisen and others have disappeared. EVOLUTION is a process of change. Charles Darwin • 1. 2. 3. 4. 5. The Theory of Natural Selection Variation exists within a population of organisms All organisms face a daily struggle to survive Those organisms with adaptations that best suit their environment have the best chance of survival & reproduction Those organisms survive & reproduce to pass on their characteristics Over time, the population changes to be best suited to their environment. Jean Baptist Lamarck • • • Stated that animals have some structures that they use frequently & others they do not use. The ones that are used frequently are strengthened & passed on. He also states that animals can acquire characteristics if they need them How Does Evolution Work? • Evolution occurs because of Natural Selection Natural Selection • • • Within a particular species, there is variation between individuals. As a result, some individuals are better adapted to their environment and are more likely to survive and reproduce. These adaptations are then passed onto the next generation. SURVIVAL OF THE FITTEST Artificial Selection • For thousands of years, humans have made use of two very important facts: 1. There is variation within a species 2. Offspring resemble their parents • • Knowing this, humans have selectively bred animals and plants for desired characteristics This is artificial selection Genetic Variation • Three main sources of genetic variation: 1. Meiosis 2. Sexual Reproduction 3. Mutations • Genetic variation is important to the process of natural selection. Remember: • Chromosomes are made of DNA & DNA consists of genes. The genes control the physical characteristics of an organism. A change in gene can lead to a change in characteristic. An Example … • The English Peppered Moth Speciation • Species: organisms that interbreed to produce fertile, healthy offspring. • Over time, the process of natural selection can cause such changes in characteristics that it leads to the formation of an entire new species. This is speciation. • It is most often caused by geographical isolation. Different characteristics arise through genetic drift, mutation and environmental pressures The isolated population is now quite different Variation of characteristics is present in population The breeding population becomes isolated The environment changes Frequency of new characteristics increases Those best suited to the environment survive Favourable characteristics are passed on New Species = SPECIATION Selection occurs Types of Evolution • Divergent Evolution – one common ancestor evolves into two species, which continue to evolve and become less and less alike over time. Types of Evolution • Parallel Evolution – Two related species arise from a common ancestor. The two species then evolve in much the same way over time, probably in response to similar environmental selection pressures. Types of Evolution • Convergent Evolution – Occurs when two or more groups that are not closely related come to resemble each other more and more as time passes. This is usually the result of occupation of similar habitats and the adoption of similar environmental roles. Types of Evolution • Which is which? Divergent Convergent Parallel Evidence for Evolution • There is a variety of evidence that supports evolution. • This includes: – – – – – Fossil evidence Comparative anatomy Comparative embryology Biogeography DNA evidence Evidence for Evolution Fossil Evidence: • Evidence for many species that existed in the past can be seen from fossilised remains of plants & animals that were once trapped during the process of rock formation. • The rock strata & the fossils in them, can be dated & arranged in sequence to show how life on Earth evolved over time. • Fossils also provided evidence about locations of continents & oceans, & the changing environments of the past. Most recent sediments Recent fossils are found in recent sediments Numerous extinct species Fossil types differ in each sedimentary rock layer New fossil types mark changes in environment Oldest sediments Only primitive fossils are found in older sediments Evidence for Evolution Comparative Anatomy: • Involves looking at the structure of limbs in birds, reptiles, amphibians & mammals. • All show similar structures suggesting common ancestry (known as homologous structures). Evidence for Evolution Comparative Embryology • Involves comparing the embryonic forms of different organisms. • Closely related organisms go through similar stages in their embryonic development, often showing similarities among structures that become so altered later in development that their common origin would not be seen in the adult form. Evidence for Evolution Biogeography • Study of geographic distribution of a species using present – day observations & the fossil record. • The distribution & evolution of a species can be affected by geographic boundaries such as mountains, lakes, oceans & deserts. Evidence for Evolution DNA Hybridisation • Most powerful piece of evidence: an organisms genetic code. • Fossil evidence suggests that the earliest forms of life were bacteria, so it seems likely that bacteria developed the code shared by all living things. • The degree to which two species differ in their genetic sequences can be measured by DNA hybridisation. DNA Hybridisation Steps: • Double – stranded DNA from each species is heated causing the strands to separate • The single – strands of DNA are ‘cut’ into smaller segments using enzymes • The segments from two species are mixed and allowed to cool together in a petri dish – any complementary bases of the two species will bond and rewind to form a double – helix • The degree to which there is there is a match between the two strands demonstrates the genetic similarity between the two species Extract human DNA Extract chimpanzee DNA Unzip the DNA using heat (both human and chimpanzee DNA unwinds at 86°C) Mix strands to form a hybrid Some of the opposing bases in the DNA sequence do not match Human Evolution Primate Classification Prosimians New World Monkeys Old World Monkeys Apes Hominids Hominids Anatomical features and habits: Bipedal with modified feet, thigh bone, pelvis, and spine Large cerebral cortex (forebrain) Reduced canines (and teeth in general) Prominent nose and chin, reduced eye ridges Body hair short or very reduced to assist cooling Highly sensitive skin Complex social behaviour Examples: Australopithecus Paranthropus Homo Ardipithecus Paranthropus boisei Homo neanderthalensis Homo sapiens Orrorin tugenensis O. tugenensis, or ‘Millennium man’ was discovered in late 2000. A new hominin from Kenya, it is claimed to be the oldest hominin yet described. Thirteen pieces, consisting of teeth, fragments of the arm, thigh bone, and a finger, from at least five different individuals have been found. The size and morphology of the teeth are intermediate between those of a chimpanzee and those of a human. Other Name “Millennium Man” Known Date 6.0 million years ago Brain Size ? cc Height ?m Physique Possibly bipedal, and a forest dweller. Little else known. Skull Shape ? Teeth and Jaws ? Geographical Kenya, Eastern Africa Distribution Ardipithecus ramidus Discovered in 1994, this species was originally thought to be an early hominin, with limited evidence of bipedalism. Two subspecies have been identified: A. ramidus ramidus (4.4 my old) A. ramidus kadabba (5.8 my old) This species is regarded by some researchers as ‘simply an ape with some unusual characteristics’. Some individuals may have been 1.2 m tall. Other fossils found with this hominin indicate that it may have been a forest dweller. Other Name Known Date Brain Size Height Physique Two subspecies: A. ramidus ramidus A. ramidus kadabba 4.4 - 5.8 million years ago ? cc c. 1.2 m Possibly bipedal forest dweller. Little else known. Foramen magnum more Skull Shape forward than apes. Teeth and Jaws Smaller, narrow molars; thinner jaw Geographica l Eastern Africa Distribution Australopithecus anamensis • • • • Anamensis was discovered at Kanapoi, Kenya in 1994. Other Name: None Known Date: 4.2 – 3.9 million years ago The find consists of complete upper and lower jaws, teeth, a piece of skull, and arm and leg bones. Brain Size: ? cc Height: ?m Anamensis had a mixture of primitive, ape-like features and advanced, human-like features. Physique: The teeth and jaws are similar to older fossil apes, but the lower leg bones show evidence of bipedalism and the upper arm bone is extremely human-like. Skull Shape: Teeth and Jaws: Geographical Distribution: Partial leg bones strongly suggest bipedalism; humerus extremely humanlike Primitive features in the skull, possibly apelike Very similar to those of older fossil apes, but canines vertical; teeth have thicker tooth enamel as in humans Eastern Africa Australopithecus afarensis Other Name ‘Lucy’, ‘First Family’ Known Date 3.9 – 2.5 million years ago Brain Size 400 – 500 cc Height 1.07 – 1.52 m Physique Skull Shape Teeth and Jaws Geographical Distribution Light build. Some apelike features: relatively long arms, curved fingers and toes, sexual dimorphism Apelike face, low forehead, bony brow ridge, flat nose, no chin Human-like teeth, canines smaller than apes, larger than humans. Jaw shape is half way between that of an ape and a human. Eastern Africa Photos courtesy of: SkullsUnlimited.com The Primitive Features of 'Lucy' This is a reconstructed skeleton of ‘Lucy’ Australopithecus afarensis – one of the earliest known bipedal hominins. The skeleton exhibits features consistent with a Jaw shape half way between V-shape of ape's and U-shape of human jaw Chest (thorax) is funnelshaped species adapted for walking bipedally .... Sexual dimorphism in the canine teeth (a primitive trait) Shoulder joint that is orientated towards the head Relatively long arms compared to legs But it also possesses many ‘primitive’ features normally associated with an arboreal existence. Wrist has high mobility Relatively short legs Ankle joint is highly mobile Finger bones are curved Toes are long and curved Redrawn from a photograph by © David L. Brill 1985 Australopithecus afarensis Small brain (410cc) Low forehead Brow ridge Large, dishshaped face Wide midface Flat nose Big, ape-like incisor Little of the skull is behind the foramen magnum Diastema (gap) Large, thickly enameled molars A Modern Human Skull (for comparison) Canines larger than in humans Australopithecus africanus Other Name None Known Date ~3.0 - 2.3 million years ago Brain Size Height 400 – 500 cc 1.1 – 1.4 m Physique Light build. Probably long arms, more ‘human’ features, probably less sexual dimorphism than A. afarensis Skull Shape Brow ridges less prominent; higher forehead and shorter face. Teeth and Jaws Geographical Distribution Teeth and jaws much larger than in humans; shape of jaw fully parabolic as in humans; canine teeth further reduced. Southern Africa Australopithecus africanus Small brain (450cc) same size as gorilla's but organization is different from an ape's No sagittal crest Brow ridge Low facial angle A Modern Human Skull (for comparison) Very large molars compared with modern humans (not shown here) Lower face protrudes forward into a snout (prognathism) Paranthropus robustus Other Name Australopithecus robustus Known Date 2.2 - 1.5 million years ago Brain Size Height Physique Skull Shape Teeth and Jaws Geographical Distribution 530 cc 1.1 - 1.3 m Heavy build. Relatively long arms. Moderate sexual dimorphism. Long, broad, flat face; crest on top of skull; moderate facial buttressing. Very thick jaws; small incisors and canines; large molar-like premolars; very large molars (megadont). Southern Africa Paranthropus robustus Small brain (530cc) Very prominent sagittal crest for the attachment of powerful jaw muscles Heavy brow ridge Part of the rear and top of this skull is missing Low facial angle Massive zygomatic arch and cheek bones Little of the skull is behind the foramen magnum A Modern Human Skull (for comparison) Small incisors (missing in this specimen) Massive molars with thick enamel are well worn suggesting a tough vegetarian diet Homo habilis Other Name Homo rudolfensis Homo habilis 2.4 - 1.6 million years ago 2 - 1.6 million years ago 600 - 800 cc 500 - 650 cc c. 1.5 m 1.0 m Robust but ‘human’ skeleton. Relatively long arms Skull Shape Larger, flatter face Small face with developed nose Teeth and Jaws Large, narrow molars; robust jaw Smaller, narrow molars; thinner jaw Eastern, and possibly Southern Africa Known Date Brain Size Height Physique Geographical Eastern Africa Distribution Homo habilis Bigger brain (650-680cc) Large variant Rounded cranium with no sagittal crest Bulge in the Broca's area of the brain for speech production Brow ridge Smaller, narrower face than the australopithecines Flat nose Small variant Projecting jaw (prognathism) More of the skull is behind the foramen magnum Jaw is less massive than in the australopithecines A Modern Human Skull (for comparison) Tooth row displays a modern curve, with narrow molars Homo erectus Other Name Homo ergaster for older African forms Known Date 1.8 - 0.3 million years ago Brain Size Height Physique Skull Shape Teeth and Jaws 750 - 1250 cc 1.3 - 1.5 m Robust but ‘human’ skeleton Flat, thick skull with sagittal keel and large brow ridge Smaller teeth than H. habilis, robust jaw in larger individuals Geographical Africa, Asia, Indonesia, Distribution and possibly Europe Homo erectus Bulge in the Broca's area of the brain for speech production Bigger brain Earliest: 850cc Latest: 1100cc Long, flattened cranium with a distinctive keel along the top Bulge in Wernicke's area of the brain for speech recognition More recent Asian forms Shelving forehead Thick brow ridge Flat face Older African forms A Modern Human Skull (for comparison) Occipital lobe (bun-like swelling) Attachment for strong neck muscles to stop the head from sagging forward Teeth are smaller than H. habilis, but more massive than our own Projecting jaw No chin Homo heidelbergensis Other Name Homo heidelbergensis Known Date Brain Size Height Physique Rhodesia skull Atapuerca skull Stenheim skull 400 000 - 100 000 years ago 1100 - 1400 cc ?m Robust but ‘human’ skeleton Skull Shape Higher cranium, less face protruding. Many regional variants with mosaics of modern and more primitive features. Teeth and Jaws Similar to H. erectus, but smaller teeth Geographical Africa, Asia, and Europe Distribution Homo heidelbergensis Large brain (1200 - 1430cc) Flat, oblong shape to the cranium Sloping forehead Large brow ridge Broad, upright face Broad nasal opening Occipital 'bun' for neck muscle attachment A Modern Human Skull (for comparison) No muzzle (no prognathism) Teeth are generally modern in form Homo neanderthalensis Other Name The Neanderthals; H. sapiens neanderthalensis Known Date 150 000 - 28 000 years ago Brain Size Height Physique Skull Shape Teeth and Jaws Geographical Distribution 1200 - 1750 cc 1.5 - 1.7 m Robust but ‘human’ skeleton, adapted for cold climates Double-arched brow ridge, high rounded orbits, midface projection, weak chin, long low skull, small mastoid process, Similar to Archaic H. sapiens; except for incisors, smaller teeth. Europe and western Asia. Homo neanderthalensis Large brain (1600cc) Larger than a modern brain but organized differently Low, long cranium Sloping forehead Double-arched brow ridge Occipital lobe (bun-like swelling) Large prominant nose and mid-facial projection Swept back, lightly built cheek bones Skull widest at the base (unlike modern skulls which are widest near the top) Powerful jaw but reduced compared to H. erectus A Modern Human Skull (for comparison) Weak chin Teeth are smaller than H. erectus, but bigger than our own Homo sapiens Other Name Early anatomically modern humans; Homo sapiens sapiens Known Date 195 000 - 60 000 years ago (for early humans) Brain Size Height 1200 - 1700 cc 1.6 - 1.85 m Physique Modern skeleton possibly adapted for warmth Skull Shape Small or no brow ridge; shorter and higher skull Teeth may be smaller; shorter jaws Teeth and Jaws than Neanderthals; chin developed Geographical Distribution Africa and western Asia (for early forms) Homo sapiens Large brain (1400cc) Convex cranial vault High, vertical forehead Skull widest high up No brow ridge, just a slight swelling of the glabella Vertical face Low, rounded occipital area Sizable mastoid process A Modern Human Skull (for comparison) Reduced tooth size with thinner enamel No muzzle (no prognathism) Sizable jaw with projecting chin Human Evolution Timeline In 2001, the 6-7 my old remains of a nearly complete skull with gorilla-like features was unearthed in Chad. Nicknamed “Toumai” and assigned to a new genus, Sahelanthropus tchadensis, scientists debate whether it is human or the remains of a proto-gorilla. Photos courtesy of: SkullsUnlimited.com Human Evolution Timeline Orrorin tugenensis, or ‘Millennium man’ was discovered in late 2000 at a site in Kenya. It is claimed to be the oldest hominin yet described. Photos courtesy of: SkullsUnlimited.com Human Evolution Timeline Originally given the name Australopithecus ramidus, it was reclassified under a new genus, Ardipithecus. Two subspecies have been identified: A. ramidus ramidus (4.4 my old) A. ramidus kadabba (5.8 my old) Regarded by some researchers as ‘simply an ape with some unusual characteristics’. Human Evolution Timeline Discovered at Kanapoi, Kenya in 1994, this earliest known species of the genus Australopithecus had a mixture of primitive, ape-like features and advanced, human-like features. Human Evolution Timeline Human Evolution Timeline Discovered in Kenya, a new genus Kenyapithecus appears to be an offshoot from the main evolutionary branches Photos courtesy of: SkullsUnlimited.com Human Evolution Timeline As many as four species from the genus Australopithecus emerge, with a wide geographic distribution, ranging from southern Africa, through East Africa, to Chad in the north. Human Evolution Timeline A group of species from the genus Paranthropus emerge in southern and eastern Africa. Superbly adapted to exploit low grade vegetarian diet, they coexist with the emerging genus Homo. Human Evolution Timeline From a probable Australopithecine ancestor emerges the first species of genus Homo. A small-brained species with fully developed bipedal locomotion, it has a talent for shaping tools from stone. This hominin does not venture out of Africa. Human Evolution Timeline What followed was an adaptive radiation of the genus Homo, leading to increased body height, brain capacity, complex social behavior, and a geographic distribution that extended well beyond Africa. Human Evolution Timeline The most recent, and perhaps most perplexing part of this emerging story, is the discovery in 2003 of what appears to be a ‘pygmy’ species of human that lived on the Indonesian island of Flores between 95 000 - 13 000 years ago.