5.4: Evolution5.4: EvolutionTopic 5: Ecology & EvolutionTopic 5: Ecology & Evolution

Miss FriedmanMiss Friedman

5.1: Definition5.1: Definition

Evolution is the cumulative change in the Evolution is the cumulative change in the heritable characteristics of a populationheritable characteristics of a population

► Darwinian Evolution is not simply based on Darwinian Evolution is not simply based on natural selection but was in fact composed of at natural selection but was in fact composed of at least five different “sub theories”least five different “sub theories”

1.1. EvolutionEvolution2.2. Common descentCommon descent3.3. GradualismGradualism4.4. Multiplication of speciesMultiplication of species5.5. Natural selectionNatural selection

1. Evolution1. Evolution

►All life is and has been perpetually All life is and has been perpetually changing. This contrasts strongly with changing. This contrasts strongly with notions that all forms of life are constant notions that all forms of life are constant and unchangingand unchanging

2. Common descent2. Common descent

►All living things share a common ancestor if All living things share a common ancestor if traced back far enoughtraced back far enough

3. Gradualism3. Gradualism

►Evolutionary change takes place slowly and Evolutionary change takes place slowly and gradually. This contrasts with saltation in gradually. This contrasts with saltation in which changes are sudden and extremewhich changes are sudden and extreme

4. Multiplication of species4. Multiplication of species

►Diversity of life is a consequence of Diversity of life is a consequence of speciation. Populations adapting to locations speciation. Populations adapting to locations and becoming reproductively isolated from and becoming reproductively isolated from other populationsother populations

5. Natural selection5. Natural selection

►A two stage process in which:A two stage process in which: Producing genetic variationProducing genetic variation SelectionSelection

5.4.2: Evidence of evolution5.4.2: Evidence of evolution

►Evolution, like any scientific theory, requires Evolution, like any scientific theory, requires evidence. evidence.

►Evidence shows that organisms change over Evidence shows that organisms change over time and even result in the production of time and even result in the production of new species of organismsnew species of organisms

►Types of evidenceTypes of evidence1. Fossil record1. Fossil record2. Homologous structures2. Homologous structures

1. Fossil Record1. Fossil Record

A fossil is the ancient preserved remains of an organism. The A fossil is the ancient preserved remains of an organism. The fossil can be dated from the age of the rock formation.fossil can be dated from the age of the rock formation.

► Sequences of fossil show the gradual change of an Sequences of fossil show the gradual change of an organism over geological timeorganism over geological time

► Although the planet Earth has extensive oceans for most of Although the planet Earth has extensive oceans for most of its existence, fish fossils have only been found in rocks for its existence, fish fossils have only been found in rocks for 500 million years (less than 15% of the Earth’s age)500 million years (less than 15% of the Earth’s age)

► No top predators such as bears and orcas existed in the No top predators such as bears and orcas existed in the time of dinosaurstime of dinosaurs

► Very few organisms today have identical form today as Very few organisms today have identical form today as hundreds of years agohundreds of years ago

2. Homologous structures2. Homologous structures

Similarities between anatomical structure Similarities between anatomical structure which are similar in form and function but which are similar in form and function but which are found in seeming dissimilar which are found in seeming dissimilar species.species.

The classic example is the pentadactyl The classic example is the pentadactyl (penta=five) and (dacytl=fingers) limb of (penta=five) and (dacytl=fingers) limb of the vertebratethe vertebrate

a)a) HumerusHumerusb)b) RadiusRadiusc)c) UlnaUlna

•In each example the bones are modified and adapted to the locomotion of the animal

•The fact that the basic shape and position of the bones is similar suggest that they have a common ancestor

•In the whale there is no real need for the fingers as they can still swim without them, this could suggest common ancestry with the other five-fingered organisms

DivergenceDivergence►The pentadactyl limb structure shows The pentadactyl limb structure shows

adaptation and modification from a common adaptation and modification from a common limb (ancestor) structurelimb (ancestor) structure

ConvergenceConvergence►Two organisms with different ancestors have Two organisms with different ancestors have

a limb structure that fulfills the same function a limb structure that fulfills the same function but has evolved from different origins.but has evolved from different origins.

►Examples are wing of a bird and the wing of Examples are wing of a bird and the wing of an insectan insect

Selective BreedingSelective Breeding►Man has selectively bred animals and plants Man has selectively bred animals and plants

for thousands of years.for thousands of years.►If an animal posses a characteristic that is If an animal posses a characteristic that is

considered useful or valuable then this considered useful or valuable then this animal is selected for breeding.animal is selected for breeding.

►The hope then is that this characteristic will The hope then is that this characteristic will be present in the next generation and at a be present in the next generation and at a higher frequency than before.higher frequency than before.

►In subsequent generations it may even then In subsequent generations it may even then be possible to select from an even more be possible to select from an even more advantageous characteristicadvantageous characteristic

Selective breeding Selective breeding continuedcontinued

►The observations of artificial selection The observations of artificial selection (selective breeding) suggested that natural (selective breeding) suggested that natural populations would:populations would: Show phenotypic variationShow phenotypic variation Be subject to natural selection pressuresBe subject to natural selection pressures There would be selection of those individuals There would be selection of those individuals

possessing the advantageous characteristicpossessing the advantageous characteristic

5.4.3: Population size & 5.4.3: Population size & evolutionevolution

► The population produces more offspring than the The population produces more offspring than the carrying capacity of the environment can support:carrying capacity of the environment can support: Offspring/population compete for limited resources Offspring/population compete for limited resources

(Intraspecific competition)(Intraspecific competition) Some individuals have characteristic (or combination) Some individuals have characteristic (or combination)

that gives them a competitive advantagethat gives them a competitive advantage These individuals are more likely to successfully These individuals are more likely to successfully

reproduce (offspring survive)reproduce (offspring survive) Through inheritance the frequency of these Through inheritance the frequency of these

characteristics become greater in the next generationcharacteristics become greater in the next generation By definition these characteristics have a genetic basisBy definition these characteristics have a genetic basis

5.4.4: Population size & survival5.4.4: Population size & survival

►Plant and animals produce far more Plant and animals produce far more offspring then could ever surviveoffspring then could ever survive Fish will lay hundreds of eggs yet only a handful Fish will lay hundreds of eggs yet only a handful

survivesurvive►Why are animal’s valuable resources wasted Why are animal’s valuable resources wasted

if they are never going to give offspring?if they are never going to give offspring?►Competition is set up for resources so only Competition is set up for resources so only

the best adapted organism will survivethe best adapted organism will survive

5.4.4 5.4.4 continuedcontinued►It should be noted that the “struggle for It should be noted that the “struggle for

survival” in this model is a consequence of survival” in this model is a consequence of over-populationover-population

►The struggle takes the form of individuals in The struggle takes the form of individuals in the population being “selected for” or the population being “selected for” or “selected against” “selected against”

►Survivors form the new breeding populationSurvivors form the new breeding population►The frequency of advantageous alleles has The frequency of advantageous alleles has

increasedincreased►The change in the heritable characteristics is The change in the heritable characteristics is

by definition evolutionby definition evolution

5.4.5: Variation in a species5.4.5: Variation in a species

►Populations of a species show variationPopulations of a species show variation►Variation means differences in phenotypesVariation means differences in phenotypes►Notice that no two humans are alike (or Notice that no two humans are alike (or

other animals)other animals)

5.4.6: Sexual reproduction & 5.4.6: Sexual reproduction & variationvariation

► Asexual (bacteria) and sexual populations both Asexual (bacteria) and sexual populations both experience mutation which increases the variation experience mutation which increases the variation within the members of a populationwithin the members of a population

► Sexual reproduction increases variation by the Sexual reproduction increases variation by the selection of mate or mutationselection of mate or mutation A fish with a better shaped mouth might be able to feed A fish with a better shaped mouth might be able to feed

on coral that cannot be accessed by other fish, he will on coral that cannot be accessed by other fish, he will have a better chance of survival into adulthoodhave a better chance of survival into adulthood

A fish mouth could be inadequately adapted and as a A fish mouth could be inadequately adapted and as a result die of starvationresult die of starvation

5.4.6 continued5.4.6 continued

►Sexually reproducing populations also Sexually reproducing populations also experience significant additional sources of experience significant additional sources of variationvariation

►There are two sources of genetic variation There are two sources of genetic variation in populations:in populations:

1. Meiosis1. Meiosis2. Fertilization2. Fertilization

1. Meiosis1. Meiosis

►When is an egg is made during meiosis, When is an egg is made during meiosis, only 50% of the mother’s information is only 50% of the mother’s information is needed.needed.

►Due to random distribution of the Due to random distribution of the chromosomes during meiosis, each egg has chromosomes during meiosis, each egg has a different combination and therefore two a different combination and therefore two eggs are never alikeeggs are never alike

2. Random fertilization2. Random fertilization

►Increases the variation in the population a Increases the variation in the population a second timesecond time

►Of the many sperm cells that exist, only one Of the many sperm cells that exist, only one will fertilize the eggwill fertilize the egg

ConclusionConclusion

►Genes get mixed up as a double lottery Genes get mixed up as a double lottery once in meiosis and a second time in once in meiosis and a second time in fertilizationfertilization

“… “… can we doubt (remembering that many can we doubt (remembering that many more individuals are born than can more individuals are born than can possible survive) that individuals having possible survive) that individuals having any advantage, however slight, over any advantage, however slight, over others, would have the best chance of others, would have the best chance of surviving and procreating their kind? On surviving and procreating their kind? On the other hand, we may feel sure that any the other hand, we may feel sure that any variation in the least injurious would be variation in the least injurious would be rigidly destroyed. This preservation of rigidly destroyed. This preservation of favourable variations and the rejection of favourable variations and the rejection of injurious variations, I call Natural injurious variations, I call Natural Selection”Selection” Darwin C. (1859)Darwin C. (1859) The Origin The Origin of Speciesof Species

5.4.7: Natural selection5.4.7: Natural selection

Natural selection is a two stage process:Natural selection is a two stage process:1. Production of variation1. Production of variation2. Selection2. Selection

5.4.7 5.4.7 continuedcontinued►When a population evolves there is a When a population evolves there is a

cumulative change in the heritable cumulative change in the heritable characteristics of the populationcharacteristics of the population

►Natural selection can act on a population Natural selection can act on a population without speciation occurringwithout speciation occurring

►In effect the genetic profile of the In effect the genetic profile of the population is adapting to changes in local population is adapting to changes in local conditionsconditions

►Ever phase in the process of evolution is Ever phase in the process of evolution is affected by variation and by selectionaffected by variation and by selection

Factors in a Factors in a Model of Model of Natural Natural

SelectionSelection

5.4.8: Examples of evolution5.4.8: Examples of evolution

1, Antibiotic resistance in bacteria1, Antibiotic resistance in bacteria2. Peppered Moth2. Peppered Moth3. New Zealand Kaka3. New Zealand Kaka

1. Antibiotic resistance in bacteria1. Antibiotic resistance in bacteria

Write a page (about 500 words) about this phenomenaWrite a page (about 500 words) about this phenomena► What is the problem?What is the problem?► How did the problem arise?How did the problem arise?► Why is this such a big issue?Why is this such a big issue?► What can we do about it?What can we do about it?

Scientific content Scientific content 10 marks10 marksWork Cited Work Cited 5 marks5 marksEffort, Spelling, Grammar etc. Effort, Spelling, Grammar etc. 5 marks5 marks

DUE THIS MONDAY MAY 25DUE THIS MONDAY MAY 25THTH