Evolution and Biodiversity Notes

Evolution

• Understanding change over time.

Biodiversity

• Biodiversity is defined as the variability among living organisms from all sources including, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part.

• This includes diversity within species, between species and of ecosystems.

Levels of Scientific Generalization

• Law

• Theory

• Hypothesis

• Observation

• Laws are general statements of great power, for which no exceptions have been found. They are, as far as we can tell, 'ALWAYS true, EVERYWHERE, ALL the time.'

• Theories can change as more evidence is collected and new technology becomes available.

• Scientific theories DO NOT become laws with more evidence.

• Laws describe WHAT happens and theories explain WHY it happens.

Phylogeny & Evolution

• Phylogeny: history of the evolution of a species or group, especially in reference to lines of descent and relationships among broad groups of organisms.

• Evolution: change in the heritable characteristics of biological populations over successive generations leading to new types of organisms.

Evidence for Evolution

• Fossil record

• Modification by descent

• Biogeography

• Genetics

Fossil Records

• The term fossil refers to any parts or impressions of an organism that may survive after its death.

• Fossils form best when organisms are buried quickly in conditions that slow the process of decay.

• Fossils are most commonly found in sedimentary rock.

• Mineral-rich hard parts (bones, teeth, shells) may remain as fossils, or minerals dissolved in water, may seep into tissues and replace the organic matter of the organism.

• On rare occasions, fossils retain organic material, as when plant material is compressed between layers of shale or sandstone.

• The fossil record is an orderly array in which fossils appear in the layers, or strata, of sedimentary rocks.

• When organisms are trapped in sediments, they record that moment in time.

• The fossils in each layer of sedimentary rock are a sample of the organisms that existed at the time the sediment was deposited.

• Because younger sediments lie on top of older ones, it is possible to determine the relative ages of fossils.

• Layers of sedimentary rock are arranged in the order in which they were deposited, with the most recent layers nearer the surface.

• Sedimentary layers can be disturbed by subsequent tectonic activity.

• The interpretation of rock layers containing fossils allows us to arrange the fossils in chronological order (order of occurrence), but does not give their absolute date.

• Only primitive fossils are found in older sediments

• New fossil types mark changes in environment

• Fossil types differ in each sedimentary rock layer

• Numerous extinct species

Geological Timeline

• A geological timeline depicts the records of diversification of life on Earth as shown by fossils

• It divides the Earth’s history from 543 million years ago up to know in THREE main eras: PALEOZOIC, MESOZOIC and CAENOZOIC

Comparative Anatomy

• The pentadactyl (5 digit) limb found in most vertebrates has the same general bone structure.

• Note that forelimbs and hind limbs have different names for equivalent bones.

• Plant and animal groups were modified to adapt their environments

Homologous Structures

• In many vertebrates, the basic pentadactyl limb has been highly modified to serve specialized locomotory functions.

• Such homologies also indicate adaptive radiation, as the basic limb plan has been adapted to meet the needs of different niches.

• The same pattern of bones comprising the pentadactyl limb can be seen on each of these examples.

• same basic plan different functions

• Had common ancestor which became adapted to live in different environments.

• Modification by descent.

• ADAPTIVE RADIATION – DIVERGENT EVOLUTION

Analogous Structures

• Not all similarities between species are inherited from a common ancestor.

• Structures that have the same function in different organisms may come from quite different origins. This phenomenon is termed analogy.

• Analogous structures do not imply an evolutionary relationship, but may indicate convergence.

• Examples:

  • Eye structure in octopus and mammals.

  • Wings in birds and butterflies.

  • Fins in fish and flippers in mammals

• Eyes in cephalopods (such as octopus) and mammals have the same function and are structurally similar but have evolved from different origins.

• hedgehogs, porcupines, & echidnas — they all have (independently-developed) spikes!

• But hedgehogs originate in Europe, porcupines come from North America, & echidnas are from Australia.

• Convergent evolution

Vestigial Organs

• Structures that serve no apparent purpose in an organism, but give clues to its evolutionary history

• Ex: whale’s pelvic bone, human coccyx, human appendix

Biogeography

• The study of the distribution patterns of organisms over space and time and the processes that produced these patterns

• Darwin used these patterns to support his theory of evolution

• PATTERNS

  • Closely related species tend to be found in same geographic region

  • Darwin and Wallace noted that different regions with similar climatic conditions contained very different animals and plants

  • Distribution of species on oceanic islands

• The Galapagos Islands - closely related

Adaptive Radiation in Galapagos Finches

• adaptive radiation in Galapagos finches

Biogeography and Continental Drift

• 250 MYA – CONTINENTS WERE JOINED TOGETHER

• Fossils of the same species can be found on the coastline of neighbouring continents

• At one time, all continents were joined (Pangea – 250 MYA)

• Geographic spread of organisms also tells of their past evolution.

• Marsupials occur in two populations today in the Americas and Australia.

• This shows the group evolved before the continents drifted apart

• Fossil evidence of the Triassic land reptile Lystrosaurus found in South America, Africa, India, Australia, and Antarctica.

• Fossil remains of Cynognathus, a Triassic land reptile approximately 3 m long.

• Fossil remains of the freshwater reptile Mesosaurus

• Fossils of the fern Glossopteris found in all of the southern continents, show that they were once joined.

• World distribution of Ratites

• Flightless birds might have developed from a common ancestor

Genetics

• Biochemical make-up of most animals remarkably similar which indicates a common ancestor.

• Evidence include:

  • Identical DNA structure.

  • Sequencing of genes.

  • Identical process of protein synthesis.

  • Common set of 20 amino acids for protein synthesis.

  • Same metabolic processes and enzymes.

  • ATP as energy-carrier.

Comparative Embryology

• Study of similarities and differences in the way organisms develop.

• Gills in cats and humans which is similar to gills in fish

• THEORY OF RECAPITULATION – the embryo of an organism will pass through all the adult stages of its ancestors.

Erasmus Darwin's Evolutionary Ideas

• Wrote book Zoonomia (1794)

• Proposed the idea of evolution:

  • All life developed from simple forms.

  • There are similarities amongst various organisms.

  • Artificial selection and metamorphosis showed how changes may have occurred

Jean Baptiste de Lamarck

• French naturalist

• Ideas in book Philosopie Zoologique (1809)

• Species were not fixed

• Develop hypothesis called Lamarckism

• Two ideas of Lamarck in explaining evolution:

  • Use and disuse

  • Inheritance of modified characteristics

• Law of use and disuse

  • Characteristic acquired due to organisms need

  • Acquired over many generations

  • Eg. Giraffes developing long necks

• Law of inheritance of modified characteristics

  • Characteristics acquired could be inherited by offspring

  • Eg. Sprinter’s children will all run fast.

Rejection of Lamarck's Theory

• Reasons for Lamarck's theory being rejected by most life scientists today

  • Theory is deterministic – Organisms evolve because they want to

  • No evidence to show that acquired characteristics are inherited by offspring

Alfred Russel Wallace

• Independently developed the theory of evolution which is similar to that of Charles Darwin.

• They jointly published an article on “Natural Selection.”

Charles Darwin's Theory of Evolution

• Develop the Theory of Evolution by Natural Selection.

• Darwin's 5-year voyage around the world in the HMS Beagle, collecting specimens and keeping notes of plants, animals seen and geography of countries visited .

• Publication of Darwin's On the Origin of the Species in 1859.

• The observations on which Darwin based his Theory of Evolution by Natural Selection:

  • Organisms of a species produce a large number of offspring.

  • The offspring show a great deal of variation.

  • Of the large number of offspring produced, only a few survive.

  • Characteristics are inherited from surviving parents to offspring.

• Organisms of a species produce a large number of offspring.

  • K-species like dogs can have litters of 5 - 12 puppies.

  • r – species like frogs will lay and fertilise a few hundred eggs.

Variation in Offspring

• The offspring show a great deal of variation.

  • In humans, there are variation in height, eye, hair and skin colour.

  • In other animals, there will be variation in aspects like patterns on the hide (e.g. giraffes and zebras).

Survival of the Fittest

• Of the large number of offspring produced, only a few survive.

• Not all offspring birthed survive to maturity.

• Many die due to factors like predation, competition, environmental resistance etc.

Inheritance of Characteristics

• Characteristics are inherited from surviving parents to offspring.

• Certain characteristics are clearly visible like eye, skin and hair colour.

• Other factors are not visible like blood group and inherited diseases.

Differences Between Lamarck’s And Darwin’s Theories

Lamarck’s Theory

Charles Darwin

Variation – individuals in population changing

Offspring show Variation shown from production

Individuals in population wanted to change

Change as a result of environmental factors

Change because individuals adapting to environment

Nature selects those that are best suited to environment

Individuals change

Population as whole change

Adaption inherited from parent to offspring

Characteristics passes on from generation to generation - enable individuals to survive

Types of Evolution

Macroevolution

• A change among species over a long time span with some species dying out and new species emerging. Major biological changes. evident in the fossil record.

Microevolution

• Evolution on the smallest scale. A generation to generation change in the frequencies of alleles within a population

Natural Selection within a population

• A population is defined as a group of individuals of the same species living and interbreeding within a given area.

Mechanisms of Microevolution

• Microevolution occurs due to variations in the "gene pool"

• Gene pool - all the alleles (alternative forms of a gene) in all the individuals that make up a population.

• It is the "pool" from which the next generation draws its genes.

Variation in the Gene Pool

• Random possibilities for change

  • Meiosis = crossing over and random assortment of chromosomes

  • Mutations = changes in genetic composition, lead to a change in the genotype, which may or may not appear in the phenotype. Galapagos finches. Can be beneficial resulting in greater chance of survival.

  • Meiosis, chance fertilisation

  • Random fertilisation = random fusion of gametes

Peppered Moth Evolution

• The evolution of the peppered moth is an evolutionary instance of directional colour change in the moth population as a consequence of air pollution during the Industrial Revolution.

• The frequency of dark-coloured moths increased at that time, an example of industrial melanism.

Genetic Drift

• Changes in the gene pool due to chance is called genetic drift.

• The smaller the population, the greater chance for random changes in frequencies.

Factors that Cause Genetic Drift

1. Bottleneck Effect

   • Drastic reductions in populations due to natural disasters or hunting leave very small population, with - different frequencies of genes. Ex. Cheetah population

2. Founder Effect

   • When a few individuals colonize an island, lake or new habitat, the population of the new colony will likely have different genetic makeup than the original larger population

Gene Flow

• Gene flow is caused by migration of individuals or their gametes between neighboring populations.

Definitions

• SPECIES: Group of organisms with large number of similar characteristics. Interbreeding can take place to produce viable offspring.

• POPULATION: Organisms of same species occupying the same habitat at the same time so that interbreeding can take place

• SPECIATION Formation of new species New species cannot breed with originally species.

Rate of Speciation

• Two theories describe the rates of speciation.

  • Gradualism

  • Punctuated equilibrium

  • Gradualism, changes in species is slow and gradual, occurring in small periodic changes in the gene pool.

  • Punctuated Equilibrium, evolution occurs in spurts of relatively rapid change with long periods of non- change.

Mechanism of Speciation

• Allopatric speciation, groups from an ancestral population evolve into separate species due to a period of geographical separation. Extrinsic to population.

  • Due to barriers or events e.g. erosion, earthquakes, volcano, continental drift. E.g. Darwin's finches

• In sympatric speciation, groups from the same ancestral population evolve into separate species without any geographical separation. Intrinsic to population. Cichlid fish over 400 species known

Macro Evolution : Speciation

• Speciation, the formation of new and distinct species in the course of evolution.

• Speciation involves the splitting of a single evolutionary lineage into two or more genetically independent lineages.

• A new species is defined as one that is reproductively isolated from the original population.

• Extinction is the termination of a kind of organism or of a group of kinds, usually a species.

• The moment of extinction is generally considered to be the death of the last individual of the species

Mechanism of Reproductive Isolation

• Temporal Isolation: Breeding at different times of the year.

• Species-specific courtship behaviour(animals)

• Adaptation to different pollinators(plants)

Temporal Isolation

• Temporal isolation means that two parts of a population reproduce at different times.

• If half of a population mates in January and the other half mates in June, they straight up won't be able to breed together.

Species-Specific Courtship Behavior

• Peacock: rattle or shake their feathers about 25 times per second, creating a rattling sound and an iridescent visual display to attract peahens' attention.

• Frigatebird: In addition to waving their heads, flapping their wings and calling to females, the males congregate in large numbers and display their vibrant red throat sacs.

• Penguins: During courtship, a male penguin will find the smoothest pebble to give to a female as a gift. If she likes the offering, she'll place it in the nest and the two will continue building up their little pebble mound in preparation for the eggs.

Adaptation to Different Pollinators

• Closely related species attempt to mate but are anatomically incompatible.

• (Example: flowering plants with pollination barriers; some plants are specific with respect to the insect pollinator, often occurs with butterflies/moths)

Sympatric Speciation

• New species develop is SAME area.

• In plants, it forms polyploid species and hybrids.

• There is a division of habitat, so individuals live in different habitats in SAME area.(niche)

• This leads to specialization in food gathering.

• Finally, sexual selection which include size, colour and patterns of mating partner.

• Above-mentioned factors become establish in population after many generations.

• Leading to a new species.

Cichlid Fish

• Many new species develop is SAME area – Lake Malawi

• There is a division of habitat, so individuals live in different habitats, rock parts and sandy bottom.

• This leads to specialization in food gathering.

• Finally, sexual selection which include size, colour and patterns of mating partner.

• Above-mentioned factors become establish in population after many generations.

• Leading to a new species.

Artificial Selection vs Natural Selection

• Nature provides variation, humans select variations that are useful.

• The intentional reproduction of individuals in a population that have desirable traits.

• Example - a farmer breeds only his best livestock – cows with large amounts of milk mating with bulls whose mother was a large milk producer

• Artificial Selection - domesticated animals (selective breeding):

• Artificial selection in plants

• The Brassicas are great examples of artificial selection. Cabbage, broccoli, cauliflower, Brussels sprouts, collards, and kale are all members of the same species, Brassica oleracea.

• Gardeners have cultivated flowers such as roses and orchids, carefully manipulating heredity to produce the “perfect” hybrid.

Differences between Natural Selection vs Artificial Selection

Natural Selection

1) Driven by nature

2) Variety centred within natural boundaries

3) Occurs in natural populations

4) Slow process - natural time

Artificial Selection

1) Driven by people

2) Variety very different from nature

3) Occurs only in domesticated populations.

4) Fast process - driven by people.

Inbreeding

• Occurs when close relations bred together.

• Used by breeder to reinforce desirable characteristics. Pedigrees and ideal crop.

• Can increase the likely hood that an individual might inherit 2 copies of a recessive allele.

• Therefore recessive genetic diseases are more likely- HOMOZYGOSITY

• Gene pool decreases

• A breed of dog call Hungarian Vishners were almost exterminated in WWII.

• Modern Vishners have a high rate of epilepsy as they stem from a small, inbred, population (genetic bottleneck)

• Cultural isolation (Jewish and Amish people).

• Common in royal families (keeps power in the family).

• Inbreeding: The breeding of related individuals within an isolated or a closed group of organisms or people.

• This increase homozygosity.

Outbreeding

• This is when individuals from a different population are brought in for breeding to increase genetic diversity.

• Often done when breeding endangered animals.

• Promotes HETEROZYGOSITY – alleles differ from each other and increases genetic variation. Hybrid vigour.

• Gene pool enlarge.

Classification Taxa

• KINGDOM Animalia

• PHYLUM Chordata

• CLASS Mammalia

• ORDER Primates

• FAMILY Hominidae

• GENUS Homo

• SPECIES Homo sapiens

Characteristics of Mammals

• The presence of hair or fur.

• Sweat glands.

• Glands specialized to produce milk, known as mammary glands.

• Three middle ear bones.

• A neocortex region in the brain, which specializes in seeing and hearing.

• Specialized teeth.

• A four-chambered heart.

Characteristics of Primates

• Flexible fingers and toes

• Opposable thumbs

• Flatter face than other mammals.

• Eyes that face forward and spaced close together. Stereoscopic or depth vision.

• Skeletal features of primates reflect an arboreal (tree living) existence.

• Large and complex cerebrum

• Social animals

Characteristics of the family Hominidae

• Males are larger than females.

• Largest primates, with robust bodies and well-developed forearms.

• Their thumb and big toe are opposable except in humans, who have lost opposability of the big toe.

• All digits have flattened nails.

• No hominid has a tail.

• Numerous skeletal differences between hominids and other primates are related to their upright or semi-upright stance.

Hominid Family Tree

• Hominid Studies

• Hominids are primate of a family(Hominidae) which includes humans and their fossil ancestors.

• Hominids are Bipedal showing a mixture of ape-like and human-like features.

• Bipedalism, fire-making, tool-making, language and culture are interdependent.

• All modern humans are genetically very closely related to each other and all primates.

Human Evolution

• Fossil remains:

  • Morphological divergence(structural changes) of homologous structures (limbs) compared to analogous structures(eye)

  • Homology leads to divergent evolution

  • Analogy leads to convergent evolution

• Genetic Evidence: mtDNA

• Archaeology : the study of human history and prehistory through the excavation of sites and the analysis of artefacts and other physical remains.

Comparing Anatomy

• Skull

• Brow ridge

• Optical plane

• Foramen magnum

• Teeth and jaws

• Cranial capacity

• Skeleton

• Overall size and posture

• Arm length/feet and hangs

Features used to classify fossils

• Position of foramen magnum – moves from rear of skull to center as humans became more upright.

• Brain capacity of skull – becomes larger in more advanced species.

• Supraorbital ridges (eye brows) – heavy ridges in older specimens ---- to flat foreheads of humans.

• Sloping forehead --- to flat forehead of modern apes.

• Possession of a snout --- from protruding to a flatter face in humans.

• Ridges on skull for muscle attachment ---become smaller.

• Shape of hard palate and lower jaw change from rectangular to a more rounded U-shape (dental arcade).

• Teeth – changing from ape-like to human:

  • Incisors change from forward pointing to more erect.

  • From larger to smaller canines.

  • From larger to smaller premolars and molars.

Ardipithecus vs Homo

• ARBOREAL

• QUADPEDAL

• MOLARS

• CANINE

• FREQUENT

Human vs Chimpanzee

• BIPEDAL

• RARE

Hominid Evolution

Australopithecus

• Australopithecus afarensis e.g. Lucy – Awash Valley Ethiopia

• Australopithecus africanus: e.g. Taung Child - Raymond Dart, Taung, Northern Cape Mrs Ples - Robert Broom, Sterkfontein Caves in Cradle of Humankind Little foot – Ron Clark – Sterkfontein Caves Latest South African finds; Australopithecus sediba possibly placed between Australopithecus and Homo species; Homo naledi, a possible candidate for earliest Homo species

Australopithecus Sediba

• A. sediba Latest find placed between Australopithecus and Homo species.

• Kingdom: Animalia

• Phylum: Chordata

• Class: Mammalia

• Order: Primates

• Family: Hominidae

• Genus: †Australopithecus

• Species: †A.Sediba

• A. sediba is considered the missing link between Australopithecus and Homo genus.

• Discovered in 2008 by Paleoanthropologist Lee Berger’s son in the Cradle of Human Kind World Heritage Site.

Homo

• Kingdom: Animalia

• Phylum: Chordata

• Class: Mammalia

• Order: Primates F

• Family: Hominidae

• Genus: Homo

• Species: H. sapiens

• Subspecies: H. s. sapiens

• Homo is the genus that includes modern humans and species closely related to them.

• The genus is estimated to be about 2.3 to 2.4 million years old, evolving from australopithecine ancestors with the appearance of Homo habilis.

Homo Fossil Locations

• H. habilis: ‘handy man’/ first tool maker: Lake Turkana (Kenya) and Olduvai gorge (Tanzania) - enlarged brain: Turkana Boy

• H. erectus: stood up straight: originated in Africa and spread to China and Java - disputed ancestor of humans and Homo neanderthalensis found in Europe.

• H. neanderthalensis: Fossils found in Europe and West Asia

• H. sapiens: Examples from Boarder Caves in KZN, Klasies river mouth. Earliest use of fire to make ochre artefacts at Blombos caves and Pinnacle Point cave(Mossel Bay)

• San: World’s oldest extant people. The San are the oldest inhabitants of Southern Africa, where they have lived for at least 20 000 years. The term San - diverse group of hunter-gatherers living in Southern Africa who share historical and linguistic connections.

Homo Sapiens : Out of Africa

• While it is generally accepted that the forerunner to Homo sapiens - Homo erectus - left Africa about 1.5 million years ago to populate other parts of the world, there are two main theories about the spread of Homo sapiens.

• The first theory, known as the 'Out of Africa' model, is that Homo sapiens developed first in Africa and then spread around the world between 100 and 200,000 years ago, superseding all other hominid species. The implication of this argument is that all modern people are ultimately of African descent.

• The other theory, known as the 'Multi-regional' Model, is that Homo sapiens evolved simultaneously in different parts of the world from original Homo erectus settlers. This means that people in China descended from the Homo erectus population there, while Australians may have descended from the Homo erectus population in South East Asia.

Multi-Regional vs. Out-of-Africa Hypotheses

• Scientists generally believe – earliest hominids developed in Africa.

• They were Homo erectus – led to 1st wave of migration of genus Homo out of Africa (+/- 1.8 mya).

• Fossil evidence shows – Homo erectus populations soon established themselves in Europe, Asia and Indonesia.

  1. Multi-regional hypothesis

  • Modern humans evolved from different groups of Homo erectus that lived in different areas of the world.

  • THUS differences among racial groups reflect the descent of each racial group from a different population of Homo erectus.

  • THUS modern Homo sapiens dates back to over 1 mya when Homo erectus migrated out of Africa.

  1. Out-of-Africa hypothesis

  • Proposes that modern Homo sapiens had its origins in one place about 200 000 years ago.

  • Then about 50 000 years ago, the species spread to the rest of the world.

  • THUS humans left Africa as modern Homo sapiens and replaced older Homo populations eg. the Neanderthals (Homo neanderthalensis) which had evolved from Homo erectus.

  • THUS the unique traits of each race represent adaptations to local conditions that arose after our species migrated out of Africa.

Evolution of Antibiotic Resistance

• “The evolution of antibiotic resistance occurs through natural selection.

• Imagine a population of bacteria infecting a patient in a hospital. The patient is treated with an antibiotic.

• The drug kills most of the bacteria but there are a few individual bacteria that happen to carry a gene that allows them to survive the onslaught of antibiotic. “

• “These survivors reproduce, passing on the gene for resistance to their offspring, and soon the patient is populated by an antibiotic resistant infection — one that not only affects the original patient but that can also be passed on to other patients in the hospital.”

Resources for Further Study

• Mind action Series pages 194 to 305. Summarise information and complete all activities as you work through the chapters.

• Answer Series pages 2.1 to 2.73.

• Attempt revision questions: Unit 1 pg 2.45 Questions 7,8,12,17,21,24,26,29 Unit 2 pg 2.53 Questions 1,4,5,17,20 PS: all questions are excellent practice questions for assessment, try to do as many as you can.