Evolution Early scientists proposed ideas about evolution Evolution

Evolution

Early scientists proposed ideas about evolution. • Evolution is a theory that explains where all the species of living things came from. – Today’s species developed from older (possibly extinct) species

Natural selection explains how evolution can occur. • There are four main principles to theory of natural selection. – Variation: individuals of a species vary in any one generation

Natural selection explains how evolution can occur. • There are four main principles to theory of natural selection. – The variations that organisms have are passed down and many of those variations are genetically controlled

Natural selection explains how evolution can occur. • There are four main principles to theory of natural selection. – overproduction: more young are produced that can survive

Natural selection explains how evolution can occur. • There are four main principles to theory of natural selection. – individuals with some genotypes are more likely to survive than others. ADAPTATION!

Natural selection explains how evolution can occur. • Conclusion – as long as the conditions remain beneficial for the trait, more individuals will have the trait in every following generation. – This is evolution by natural selection

Natural Selection • Theory proposed by Charles Darwin & Alfred Wallace • Both influenced by earlier ideas by Charles Lyell’s Principles of Geology – Geological processes were slow and uniform If Earth can change slowly, then plants and animals might be able to also

Darwin observed differences among island species. – Galápagos tortoises that live in areas with tall plants have long necks and legs; wet areas with short plants have shorter necks – Galápagos finches that live in areas with hard-shelled nuts have strong beaks; those that eat fruit have more delicate beaks. – These observations and ideas led him to publish On the Origins of Species by Means of Natural Selection

Several key insights led to Darwin’s idea for natural selection. • Darwin wasn’t familiar with Mendel’s work, so he didn’t understand how genetics might be involved • He thought animals could change their form because he saw animal breeders do that through artificial selection • Artificial selection is a process where humans select traits through breeding. neck feathers crop tail feathers

Where else do we see artificial selection?

Donkey + Horse =

• Today we have examples of natural selection – Industrial melanism (increased amount of dark pigmentation) in Biston betularia (Peppered Moth) – Antibiotic resistance in bacteria non-polluted forest

• Survival alone is not enough an animal must have children! This way, its “successful” genes can be passed on • Overproduction not necessarily a good thing – Starling bird study – Optimal number of eggs to lay was 4 -5 – Laying 9 -10 eggs was not a good strategy • Decreased protein/cytoplasm in each egg • Hatchlings came out smaller • Did not survive as long • “Survival of the fittest” meant the more you are able to reproduce successful offspring, the more evolutionarily successful you are!

Old and New Theory Lamarckism (“acquired traits”) - Acquired traits can be passed on to offspring - the more you used something the stronger /bigger it will be - Giraffes stretch out their necks to reach for food, so their young will also have longs necks NOT TRUE: if you get a tattoo… will your children be born with it?

Old and New Theory • Punctuated Equilibrium (S. Gould) – Evolution is episodic, not slow and smooth • Animals remain unchanged until a sudden change in the environment (i. e. , natural disasters) • episodes of speciation occur suddenly in geologic time • followed by long periods of little evolutionary change – Evidence • Fossil record • Species go extinct then replaced by other species

Evidence for evolution • Fossil Record: If living things evolved, we should see a record of this evolution preserved as fossils (preserved evidence of life) See geologic time scale: What causes breaks? – Simplest organisms appear first • Paleozoic: simple marine organisms • Mesozoic: reptiles & flowering plants • Cenozoic: birds & mammals dominate

Precambrian • Archean – Early life – Photosynthetic bacteria

Precambrian • Proterozoic – Eukaryotes arise

Paleozoic Era

Mesozoic

Cenozoic

Evidence for evolution • This timescale supports evolution, just not a slow and smooth one as Darwin suggested – There are no smooth transitions – One animal seemed to be replaced by anotherefore, punctuated equilibrium is the best explanation

Evidence for evolution • Comparative Anatomy: Homologous vs. Analogous – Homologous structures: body parts that are similar and are believed to have a common ancestor

Homologous Structures

Evidence for evolution • Comparative Anatomy: Homologous vs. Analogous – Homologous structures: body parts that are similar and are believed to have a common ancestor • Function is different – The strong similarity suggests evolution! • One original ancestral organ has been modified in various ways to produce the various homologous structures of today

• The study of anatomy provides evidence of evolution. – Analogous structures have a similar function. – Analogous structures are not evidence of a common Human hand ancestor. Mole foot – Show convergence of species; something in their environment pressured them to evolve specialized structures Fly wing Bat wing

Evidence for evolution • Analougous Structures – Look the same and may have the same function, but not related, and do NOT have a common ancestor

Analogous Structures

Evidence for evolution • Analougous Structures – Look the same and may have the same function, but not related, and do NOT have a common ancestor – Show convergence where two unrelated organs come to look alike

Structural patterns are clues to the history of a species. • Vestigial structures are remnants of organs or structures that had a function in an early ancestor. • Ostrich wings are examples of vestigial structures.

Evidence for evolution • Vestigial organs – “left-overs” that were functional in some other related organism, but are useless now

Evidence for evolution • Vestigial organs – “left-overs” that were functional in some other related organism, but are useless now Suggests that these organisms were descendents of other organisms with legs

Evidence for evolution • Embryology – Embryos of many vertebrates look the same at an early stage • Gill slits • Tails (may disappear as adults) “Ontogeny recapitulates phylogeny” The embryo “reviews” the whole evolutionary or development history of the organism (phylogeny) as is undergoes its individual embryological development (ontogeny)