8.8 / 8.9 magnitude earthquake

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Tsunami strikes Japan - 10-meter high wave

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Tsunami strikes Japan

Hawaii orders evacuation of low-lying coastal areas after massive earthquake off Japan triggered tsunami alert

Tsunami warning for all the Pacific!

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Tsunami warnings…

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Let’s review: Natural Diversity By the Numbers –

Estimated 2 - 100 million species, with a best estimate of somewhere near 10 million

~1.4 million described species ~1 million described insects/ 350,000 described beetles 8,800–10,200 living bird species ~5,500 species of mammals

Great diversity exists, with each species exhibiting a considerable degree of suitability for its natural lifestyle

How? Seems unlikely

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What is evolution?

Broad: The gradual process by which the living world has been developing following the origin of life.

Narrow: Change in the genetic frequencies of a population.

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Why is the theory of evolution important? Implications for people:

Antibiotic resistance, pesticide resistance, control of disease, human epidemiology, development of new crops, medical treatments, conservation biology, etc. (not to mention the ecological implications)

Evolution provides the mechanism to address these issues.

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Fossil Record (The fossil record provides snapshots of the past that, when assembled, illustrate a panorama of evolutionary change over the past four billion years. The picture may be smudged in places and may have bits missing, but fossil evidence clearly shows that life is old and has changed over time.)

Morphology Vestigial organs (A vestigial organ or structure is any organ or structure

found in a species which is not being used as it is in other species. Contrary to popular belief, vestigial organs and vestigial structures aren't necessarily useless or functionless.)

Biogeography (study of the distribution of species (biology) spatially (geography)

and temporally (history).) Molecular evidence (All living things are fundamentally alike. At the cellular

and molecular level living things are remarkably similar to each other. These fundamental similarities are most easily explained by evolutionary theory: life shares a common ancestor. )

Evidence for evolution

Early fossil discoveries

Nicholas Steno's anatomical drawing of an extant shark and a fossil shark tooth. Nicholas Steno's anatomical drawing of an extant shark (left) and a fossil shark tooth (right). Steno made the leap and declared that the fossil teeth indeed came from the mouths of once living sharks.

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In the 17th century, Nicholas Steno: similarity between shark teeth and the rocks commonly known as "tongue stones". - first understanding that fossils were a record of past life.

Two centuries later, Mary Ann Mantell picked up a tooth, which her husband Gideon thought to be of a large iguana, but it turned out to be the tooth of a dinosaur, Iguanodon. - many fossils represented forms of life that are no longer with us today.

Transitional forms

A skull of the gray whale that roams the seas today has its nostrils placed at the top of its skull. It would appear from these two specimens that the position of the nostril has changed over time and thus we would expect to see intermediate forms.

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Pakicetus is described as an early ancestor to modern whales. Although pakicetids were land mammals, it is clear that they are related to whales and dolphins based on a number of specializations of the ear, relating to hearing. The skull shown here displays nostrils at the front of the skull.

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Evidence for evolution: Fossil record

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Jaw bone evolution from therapsid reptiles to mammals.

Evidence for evolution: Fossil record

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Evolution through time: Variation through geologic periods.

Fossils in most recent strata are often similar if not indistinguishable from living species.

The older the strata is, the more different the fossils.

Evidence for evolution: Fossil record

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Evidence for evolution

Morphology: This was how

species were described as “related” as far back as 18th century.

Linnaean hierarchy: From Kingdom to

sub-species

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Evidence for evolution

Vestigial Structures: Structures that are not fully functional or functional

at all.

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Vestigial Structures Blind cave dwelling animals still have eyes (that

don’t work). Why does an ostrich have wings?

Evidence for evolution

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Evidence for evolution: Biogeography Biogeography: the geographic

distribution of organisms

those [organisms] of the Cape de Verde Islands bearing the impress of Africa, as the inhabitants of the Galapagos Archipelago are stamped with that of America.

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Evidence for evolution: Biogeography Evolution through space:

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Gondwana

Evolution through time and space

EFFECTS OF CONTINENTAL DRIFT ON ECOLOGY OF EVOLUTION

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The history of life can be gauged by the geological time scale.

Ecologists recognize key features of the geological record: earth formed 4.5 billion years ago life arose within the first billion years life remained primitive for most of earth’s history ancient physical environments were quite different

from those of the present: the early atmosphere had little oxygen and early microbes

used anaerobic metabolism increased oxygen led to diversification of complex life forms

The Geologic Record

About 590 Mya, most of the modern phyla of invertebrates appeared in the fossil record: these early animals began to protect themselves with

hard shells, which make excellent fossils the Paleozoic era is thus the first of three major

divisions of geologic time reflecting diversification of animals: Paleozoic: 590 Mya to 248 Mya Mesozoic: 248 Mya to 65 Mya Cenozoic: 65 Mya to present

Continental Drift

The continents are islands of low-density rock floating on the denser material of the earth’s interior and carried along by convection currents: the movements of the continents over time are called

continental drift These movements have two important ecological

consequences: positions of continents, ocean basins influence climate continental drift creates and breaks barriers to dispersal

Continental Drift: Mesozoic to Present

In the early Mesozoic era, 200 Mya, continents formed a single giant landmass called Pangaea

By 144 Mya (beginning of the Cretaceous period) the northern continents (Laurasia) had separated from the southern continents (Gondwana) at this time Gondwana itself was also breaking apart

By the end of the Mesozoic era (65 Mya), South America and Africa were widely separated, and many other patterns were emerging.

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Continental drift

Consequences of Continental Drift Details of continental drift have yet to be

resolved, but implications for evolution of animals and plants are clear; for example: the distributions of the flightless ratite birds (such as

ostriches) are the results of connection between the southern continents that made up Gondwana: these birds are descended from a common Gondwanan

ancestor splitting of a widely distributed ancestral population by

continental drift is called vicariance

Lineages of ratite birds were separated by the fragmentation of Gondwana – 80 mya. Evolutionary relationships of these birds reconstructed from DNA sequences

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(A)Large flightless birds

(B) the phylogenetic tree of the flightles birds

(C)Ostrich (left) is African; rhea (middle) is found in similar grasslands in South America; the emu (right) in Australia

Analogous: similar in superficial form or function

Homologous: derived from an equivalent structure in a common ancestry

EVOLUTION: CONVERGENT AND PARALLELS

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Convergence

Convergence is the process whereby unrelated species living under similar ecological conditions come to resemble one another more than their ancestors did:

Analagous but not homologous there are numerous examples of convergence:

woodpecker-like birds that fill the woodpecker niche in many systems lacking woodpeckers

similarities of plants and animals of North and South American deserts

similar body forms of dolphins and penguins, which both resemble tuna, whose swimming lifestyle they share

Convergent evolution

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Wings of bats and birds – similar in form/function but not from a common ancestry; structurally different

Pairs of unrelated African and South American rain forest mammals: similar lifestyles and adaptations; striking convergence

Parallel evolution

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Ancestrally related groups – then isolated from each other

In contrast to convergent evolution, diversified from a common ancestral line and both inherited a common set of potentials and constraints

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Parallel evolution of marsupial and placental mammals:

Pairs of species are similar in both appearance and habit and usually (not always) in lifestyle

To recap

Convergent Evolution Convergent evolution takes place when

species of different ancestry begin to share analogous traits because of a shared environment or other selection pressure. For example, whales and fish have some similar characteristics since both had to evolve methods of moving through the same medium: water.

Parallel Evolution Parallel evolution occurs when two

species evolve independently of each other, maintaining the same level of similarity. Parallel evolution usually occurs between unrelated species that do not occupy the same or similar niches in a given habitat.

(a) divergent (b) convergent (c) parallel

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Evidence for evolution

Molecular evidence the more closely related two organisms are, the

more similar are their genetic structure.

Often times, morphological traits can be ambiguous.

One of the most important sources of information on phylogenetic relationships

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Maintaining Genetic Variation –

Without Selection: no loss or gain (random) B. Hardy-Weinberg Theorem: constant allelic

frequencies are maintained if ... populations are large, individuals contribute equally to genetic composition of

next generation, and matings are random

Remember: Narrow definition of evolution = change in the genetic frequency of a population.

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Why does this matter?

If population is not at equilibrium – There are outside forces acting on the population.

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Outside forces that can change population genetics. Mutations

origin of variations, and mutation increases under stress Age, chemicals, UV-radiation

Migration Population size Non-Random Mating

Nonrandom Mating: ∆ gene frequencies Environmental Variance: favor some phenotypes Effects of Selection: stable polymorphisms

Natural Selection

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Loss of Genetic Variation

Inbreeding: rapid loss of genes Fixes traits quickly

Genetic Drift: random losses of genes Neighborhoods: local breeding tendency

Races of plants and animals Bottlenecks: low population = reduced pool,

duration of the low population is critical (drift)

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• Survivors of a near-extinction resulted in close inbreeding 10,000 years ago.

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Current Evolution

According to narrow definition: Evolution is little more than a process that

changes gene frequencies in a non-random manner;

environmental influences direct this change What are a few examples of recent evolution

of species that can be correlated to an environmental stress?

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Examples

The evolution of pesticide resistence in pest species

The evolution of antibiotic resistence in human pathogens

note the recent discovery of plague and tuberculosis exhibiting broad-spectrum antibiotic resistence

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Insect species resistant to pesticides

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Strep resistance to penicillin

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Maintenance of variation

So how is variation maintained in the face of environmental pressures and natural selection?

Ever see a constant environment? Microenvironmental differences exist over small

spatial scales. Temporal heterogeneity is a common

characteristic of physical environments.

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“There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that whilst this planet has gone cycling on according to the fixed laws of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.” Charles Darwin – The Origin of Species (Last

sentence)

END OF CHAPTER 2

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ADDITIONAL INFORMATION

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Genetics review

The phenotype is the outward expression of an individual's genotype Genotype: unique genetic constitution Phenotype: outward expression of that genotype A genotype = set of genetic instructions; blueprints Phenotype = the expression of that genotype in the

form of an organism (is that enough? Are there external factors?)

Effects of environmental influences are like details in a blueprint that are left to the discretion of the building contractor.. What does that mean?

More genetics

All phenotypic traits have: Genetic basis + influence by variations in the

environment What kind of environmental variations?

Phenotypic plasticity Capacity of an individual to exhibit different

responses to its environment How the individual responds to environmetnal

variation

Genetic variation (review, right?) Alleles

Different forms of a particular gene Heterozygous

Two different alleles for a particular gene Homozygous

Both copies of a gene are the same

Dominant… Recessive… Gene pool

All the alleles of the genes of every individual in a population

Sources of genetic variation

How does genetic variation arise? Mutation

Any change in the sequence of the nucleotides that make up a gene or in regions of the DNA that control the expression of a gene

Consequence? Drastic – maybe lethal – changes in the phenotype No detectable effect – silent mutations New phenotypes produced better suited to the local

environment phenotypes increase Multiple effects pleiotropy (effects of a single gene on

multiple traits)

Genetic basis of continuously varying phenotypic traits

Many phenotypic traits with ecological relevance vary continuously over a range of values (eg: body size)

Adaptations result from natural selection on heritable variation in traits that effect evolutionary fitness The most important consequence of genetic

variation for the study of ecology is evolution by natural selection

Evolution Any change in a population’s gene pool (what is a

gene pool?) Individuals whose traits enable them to have higher

rates of reproduction have more offspring alleles increase

Adaptations or evolutionary adaptation Process = adaptation

Adaptation (process of evolution by natural selection)1. Variation among individuals

Eg – bird beaks; different individuals have different-sized beaks

2. Inheritance of that variation Size of bird’s beak has an existence of its own in

a population; individual is borrowing that trait

3. Differences in survival and reproductive success (or fitness) related to that variation

Fitness: production of descendants over an individual’s lifetime.

+Evolutionary change

Change in a California citrus pest

Cyanide fumigation no longer effective

Stabilizing, directional, and disruptive selection Stabilizing selection

Individuals with intermediate (average) phenotypes have higher reproductive success Population moved towards an optimum point Maintains a single fittest phenotype When the environment of a population is relatively unchanging: dominant mode; little

evolutionary change Directional

Fittest individual have a more extreme phenotype; When new optimum reached – becomes stabilizing selection

Disruptive Increase genetic and phenotypic variation within a population and in the extreme case

creates a bimodal distribution of phenotypes; relatively uncommon; eg: individuals specializing on one of a small number of food resources; strong competition among individuals

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Example of

Disruptive selection

Population genetics and the prediction of evolutionary change Population genetics

Study of the dynamics of natural selection and genetic change in populations

Populations are continually engaged in dynamic evolutionary relationships with their environment that shape their ecological interactions

(one) Goal of population genetics to develop methods for predicting changes in gene frequencies in response to selection

Why?Ability to predict them can tell us whether the genetic changes we

observe are consistent with our understanding of evolution(check out the ‘more on the web’ links)

Population genetics and ecologists

1. every population harbors some genetic variation that influences fitness .. Potential for evolution exists in all populations

Except?2. Changes in the environment will almost always be met

by an evolutionary response that shifts the frequencies of genotypes within the population. (translate?)

Magnitude of the evolutionary response depends on genetic variation present in the pop at a given time

3. Rapid environmental changes brought about by the appearance of new adaptations in populations of enemies or by human-caused changes in the environment (eg?) can exceed the capacity of a population to respond by evolution

So?