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This text explores the concept of homologies and analogies as evidence of common ancestry in organisms. It discusses how homologous structures, molecular genetics, developmental similarities, and vestigial structures provide insight into evolutionary relationships. The text also introduces the concept of cladograms to depict these relationships.
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7A – Evidence of Evolution Homologies and Analogies
TEK 7A • 7A analyze and evaluate how evidence of common ancestry among groups is provided by the fossil record, biogeography, and homologies, including anatomical, molecular, and developmental.
Which two organisms are closely related to each other? Shark and Dolphin Or Cauliflower & Broccoli WHY????
Homologous Structures • traits inherited by two different organisms from a common ancestor • Sometimes different function, but same structure • How do you know that these four organisms are related?
Although the organisms do not resemble each other from the outside or even perform the same functions, on the inside the structure is the same in the limbs.
Homologous Body Structures Section 15-3 Turtle Alligator Bird Mammal Ancient lobe-finned fish • Just because they have the same structure does that mean they: • Look the same on the outside? • Live in the same habitat? • Eat the same type of food?
Analogous Structures • Two very different organisms evolve a similar function or characteristic independently of one another due to similar environmental challenges, not common ancestry • Same function, different structures
Of Shrimp and Snailsanalogous or homologous? Analogous: Inside their shells are very different: Barnacles and limpets have many superficial similarities: both are small creatures with conical shells and can be found in the ocean on rocky shores….so analogous or homologous?
Which one below has the insides of a shrimp and which has the insides of a snail? • Barnacles Limpets
So does that mean they had a common ancestor whose was closely related to them? • Who do you think was the ancestor of barnacles and limpets? Talk with your partner (30 sec).
WHY are they not closely related??? • The common ancestor had no conical shell. • Similar shells evolved because both lineages faced a similar challenge: • a rocky, wave-swept environment teeming with predators ready to pry a small creature off a rock for lunch — and conical, hard-to-get-a-grip-on armor offers a lot of protection in such an environment. These lineages evolved their shells independently — meaning that the shells of these two lineages are analogies.
Molecular – Genetics Similarities in DNA • DNA and protein (amino acid) sequences suggest common ancestry.
Why grow a tail and then lose it? HUMAN EMBRYO _________________ _________________ _________________ has a tail at 4 weeks Tail disappears at about 8 weeks tail http://www.suite101.com/files/topics/6234/files/tail_HumanTail.gif
Developmental - Embryology • Embryonic Structures Of Different Species Show Significant Similarities • Embryo – early stages of vertebrate development
Vestigial Structures • Vestigial Structures: • No useful function • Ex: hipbones in whales & boa constrictors or tail & appendix in humans
Vestigial Structures • What other structures can you think of that are considered vestigial? • Turn and talk with your partner: (30 sec)
What do you think were some uses of these now vestigial structures? • Remember!!!! • These structures were once very useful.
Cladogram - diagram that shows the evolutionary relationships among a group of organisms
Concept Attainment Quiz • Students will fill out graphic organizer • Teachers see notes below
Complete “Out” for Homework!!! • Complete packet with your neighbors. DUE TODAY - Get busy • QUIZ NEXT CLASS!!!
