Evidence for Evolution Topic 5.1

Understanding: Evolution occurs when heritable characteristics of a species change. *There is evidence that characteristics of species change over time. Acquired characteristics = develop after birth Heritable characteristics = already present at birth Evolution = change in heritable characteristics Natural Selection = the mechanism of evolution “evolution BY natural selection”

3 types of evidence for evolution: Fossil record Selective breeding of domesticated animals Homologous structures

Understanding: Fossil record provides evidence for evolution

Paleontology = study of fossils

Evidence for evolution from fossil record: Rock layers are deposited from the bottom up Therefore we can determine RELATIVE AGE of fossils We can also determine ABSOLUTE AGE of fossils through radioisotope dating (such as carbon dating) of the rocks In rock layers from bottom up: bacteria, algae, fungi, worms, bony fish, amphibians, reptiles, birds, mammals (110 mya) Plant fossils occur before animal fossils Extensive sequence of fossils, linking related organisms together

Trilobites! Extinct species of marine arthropods First appeared in early Cambrian era (521 mya), flourished during Paleozoic era, completely extinct by Permian era (250 mya) One of most successful animals, living in ocean for over 250 my Over 17000 species

Missing Links! “missing links” = gaps in fossil record E.g. link between reptiles and birds Dilong paradoxus = feathered dinosaur “emperor dragon paradox” Fossil found in China Lived 130 mya 5 ft tall, 25 pounds

Understanding: selective breeding of domesticated animals shows that artificial selection can cause evolution Domesticated breeds of livestock and pets have not always existed in their current form Artificial selection = the process of humans repeatedly selecting for and breeding animals and plants with traits most suited for or desired by humans Artificial selection causes considerable changes in domesticated animals over relatively short period of time Shows that “selection” can cause evolution (but doesn’t prove evolution has actually occurred through “natural” selection)

Over the last 15,000 yrs many breeds of dog have been developed by artificial selection from domesticated wolves

Artificial Selection examples:

Where did all these similar veggies come from?

Understanding: evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function

Convergent vs Divergent evolution

Adaptive radiation = a process in which organisms diversify rapidly into many new forms, particularly when a change in the environment makes new resources available, creates new challenges and opens environmental niches.

…homologous structures Do not prove organisms evolved Do not prove common ancestry Do not explain the mechanism of evolution But they are difficult to explain without evolution E.g. why do we have an appendix? Could be explained by evolution as something no longer with a function and is gradually being lost.

Nature of Science: looking for patterns, trends & discrepancies: there are common features in bone structure of vertebrate limbs despite their varied use * Varied use of vertebrate limbs: walking, running, jumping, flying, swimming, grasping, digging, tearing * Varied uses require different joints, different amounts of force, different features * However, there is a pattern: common bone structure despite different functions! * The pattern: pentadactyl limbs * Patterns require explanation * Only reasonable explanation proposed so far is evolution from a common ancestor

Application: Comparison of the pentadactyl limb of mammals, birds, amphibians & reptiles with different methods of locomotion

Understanding: populations of a species can gradually diverge into separate species by evolution Species = a group of organisms which can interbreed and produce fertile offspring Speciation = evolutionary process by which new species arrive How? Two populations of same species separate (geographically or biologically) Natural selection acts differently on the two, so they evolve in different ways (they diverge) 3. After time, if they can no longer interbreed, they are 2 different species

Here’s a speciation example from U of Cal at Berkeley: http://evolution.berkeley.edu/evosite/evo101/VBDefiningSpeciation.shtml

The scene: a population of wild fruit flies minding its own business on several bunches of rotting bananas, cheerfully laying their eggs in the mushy fruit...

Disaster strikes: A hurricane washes the bananas and the immature fruit flies they contain out to sea. The banana bunch eventually washes up on an island off the coast of the mainland. The fruit flies mature and emerge from their slimy nursery onto the lonely island. The two portions of the population, mainland and island, are now too far apart for gene flow to unite them. At this point, speciation has not occurred—any fruit flies that got back to the mainland could mate and produce healthy offspring with the mainland flies.

The populations diverge: Ecological conditions are slightly different on the island, and the island population evolves under different selective pressures and experiences different random events than the mainland population does. Morphology, food preferences, and courtship displays change over the course of many generations of natural selection.

So we meet again: When another storm reintroduces the island flies to the mainland, they will not readily mate with the mainland flies since they’ve evolved different courtship behaviors. The few that do mate with the mainland flies, produce inviable eggs because of other genetic differences between the two populations. The lineage has split now that genes cannot flow between the populations.

Allopatric vs Sympatric speciation Allopatric speciation = species separated geographically, then become 2 different species Sympatric speciation = species in same geographic location, but separated biologically into 2 diff groups because of 2 different preferences (habitat, diet, niche, etc), therefore reducing gene flow between the 2 groups until they are 2 different species

Sympatric or allopatric?

Endemic species = species found only in a certain geographical area E.g. lava lizards are endemic to Galapagos Islands (similar lizards on nearby islands, but diff species) What are some endemic species to Florida? http://www.landscope.org/florida/plants-animals/lists/

Gradual vs Punctuated divergence?

Understanding: continuous variation across the geographical range of related populations matches the concept of gradual divergence Continuous range of variation between populations = evidence for origin of new species by evolution Willow ptarmigan of Norway vs red grouse of Britain

Continuous variation in Galapagos Finches

Application: development of melanistic insects in polluted areas. Peppered moth activity Melanistic = dark varieties of typically light-coloured insects Biston betularia = peppered moth Demonstrates changes in allele frequencies over time due to natural selection

Peppered moth example demonstrates changes in allele frequencies over time due to natural selection

Melanistic ladybugs! Where would they be more common?

There are many misconceptions! http://evolution.berkeley.edu/evolibrary/misconceptions_faq.php

Charles Darwin Published Origin of Species by Means of Natural Selection in 1859 Throughout his book, he did not use the word “evolution” Instead “decent with modification by means of natural selection” Darwin used the word evolution one time, on the last line: 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 circling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved. [Abridged version of Origin of Species]