Chapter 6Chapter 6

Adaptations Over TimeAdaptations Over Time

Ch 6.1Ch 6.1 - Evolution - Evolution

A. A. EvolutionEvolution – changes in inherited – changes in inherited characteristics of a species over timecharacteristics of a species over time

1. A 1. A speciesspecies is a group of organisms that is a group of organisms that share similar characteristics and can share similar characteristics and can produce fertile offspringproduce fertile offspring

B. Early Models of EvolutionB. Early Models of Evolution

1. 1. Acquired characteristics Acquired characteristics – proposed by – proposed by Jean Baptiste de LamarckJean Baptiste de Lamarck

2. Suggested that traits developed during 2. Suggested that traits developed during an organisms life time could be inherited an organisms life time could be inherited by future offspringby future offspring

3. This theory was not supported by 3. This theory was not supported by evidenceevidence

C. Darwin’s Model of EvolutionC. Darwin’s Model of Evolution

1. Charles Darwin observed that species of 1. Charles Darwin observed that species of finches on the Galapagos Islands looked finches on the Galapagos Islands looked similar to mainland finch speciessimilar to mainland finch species

2. Darwin hypothesized that plants and animals 2. Darwin hypothesized that plants and animals on the Galapagos Islands off the coast of on the Galapagos Islands off the coast of South America originally came from Central South America originally came from Central and South Americaand South America

3. He reasoned that members of a 3. He reasoned that members of a population best able to survive and population best able to survive and reproduce will pass their traits to the next reproduce will pass their traits to the next generationgeneration

4. Over time these differences result in 4. Over time these differences result in new speciesnew species

5. Darwin’s hypothesis became known as 5. Darwin’s hypothesis became known as the theory of evolution by the theory of evolution by natural natural selectionselection

“ “ Organisms with traits best suited Organisms with traits best suited to their environment will more likely to their environment will more likely survive and reproduce.”survive and reproduce.”

D. D. VariationVariation – an inherited trait that makes – an inherited trait that makes an individual different from other an individual different from other members of its speciesmembers of its species

1. An 1. An adaptationadaptation is a variation that makes is a variation that makes an individual better suited to its an individual better suited to its environmentenvironment

2. Many environmental factors can cause 2. Many environmental factors can cause changes in the sources of geneschanges in the sources of genes

3. Geographic isolation can make 2 3. Geographic isolation can make 2 populations so different that they can populations so different that they can become different speciesbecome different species

E. Speed of EvolutionE. Speed of Evolution

1. 1. GradualismGradualism – describes evolution as a – describes evolution as a slow, ongoing processslow, ongoing process

2. 2. Punctuated Equilibrium Punctuated Equilibrium – model says – model says gene mutation can result in a new species gene mutation can result in a new species in a relatively short timein a relatively short time

Ch 6.2 Ch 6.2 – Clues About Evolution– Clues About Evolution

A. Direct Evidence of EvolutionA. Direct Evidence of Evolution

1. 1. FossilsFossils – found in sedimentary rock – found in sedimentary rock show that living things evolvedshow that living things evolved

2. 2. BacteriaBacteria – development of antibiotic – development of antibiotic resistance in bacteriaresistance in bacteria

B. Fossils age can be determined by 2 B. Fossils age can be determined by 2 methods:methods:

1. 1. Relative Dating Relative Dating – looks at fossil – looks at fossil location in particular layer of rock; location in particular layer of rock; older older rock layers are under newer rock layers are under newer rock layersrock layers

2. 2. Radiometric & Carbon Dating Radiometric & Carbon Dating – – compares the amount of radioactive compares the amount of radioactive element or carbon with the amount that element or carbon with the amount that does not contain thesedoes not contain these

C. Fossil records have gapsC. Fossil records have gaps

1. Incomplete rock record b/c most 1. Incomplete rock record b/c most organisms do not become fossilsorganisms do not become fossils

2. Enough fossils have been discovered 2. Enough fossils have been discovered for scientists to conclude that complex for scientists to conclude that complex organisms appeared after simpler onesorganisms appeared after simpler ones

3. Most organisms that have ever existed 3. Most organisms that have ever existed are now extinctare now extinct

D. Indirect Evidence of EvolutionD. Indirect Evidence of Evolution

1. 1. EmbryologyEmbryology – the study of embryos – the study of embryos and their development shows similarities and their development shows similarities among all vertebrate speciesamong all vertebrate species

2. 2. Homologous body parts Homologous body parts – can indicate – can indicate that 2 or more species share a common that 2 or more species share a common ancestorancestor

3. 3. Vestigial Structures Vestigial Structures – structures that do – structures that do not seem to have a function but might not seem to have a function but might have once functioned in an ancestorhave once functioned in an ancestor

4. 4. DNADNA – can provide evidence about how – can provide evidence about how closely related organisms areclosely related organisms are

Ch 6.3 Ch 6.3 – Evolution of Primates– Evolution of Primates

A. A. PrimatesPrimates – group of mammals with – group of mammals with opposable thumbs, binocular vision and opposable thumbs, binocular vision and flexible shouldersflexible shoulders

Lemurs, Tarsiers, Monkeys, Apes & Humans

1. 1. HominidsHominids - appeared about 4-6 million - appeared about 4-6 million years ago and had larger brains than years ago and had larger brains than apesapes

2. Fossils such as 2. Fossils such as AustralopithicusAustralopithicus point to point to Africa as the origin of hominidsAfrica as the origin of hominids

3. 3. Homo habilis Homo habilis and and Homo erectusHomo erectus – are – are thought to be early human ancestorsthought to be early human ancestors

B. B. Homo sapiens Homo sapiens – “Wise Human” began – “Wise Human” began evolving about 400,000 years agoevolving about 400,000 years ago

1. 1. NeanderthalsNeanderthals – had short, heavy – had short, heavy bodies with thick bones, small chins and bodies with thick bones, small chins and heavy brow ridgesheavy brow ridges

a) Disappeared about 30,000 years agoa) Disappeared about 30,000 years ago

b) Not thought to be a direct ancestor to b) Not thought to be a direct ancestor to modern day humansmodern day humans

2. 2. Cro-Magnon humans Cro-Magnon humans – fossils date from – fossils date from around 10,000-40,000 years agoaround 10,000-40,000 years ago

a) Are thought to be a direct ancestor to a) Are thought to be a direct ancestor to early early Homo sapiensHomo sapiens