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Questions and Answers
What is the function of the appendix in modern humans?
What is an example of an atavistic feature?
What is an analogy in biology?
What is an example of homologous structures?
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What is the term for the process of different species developing similar characteristics due to similar selection pressures?
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What is the primary reason why species that share a common ancestor have some features in common?
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What is the term for a trait that is similar due to common ancestry?
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What is the concept that explains why evolution acts on the existing body form and adds variations to it?
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What is the term for structures that have no apparent function and appear to be residual parts from a common ancestor?
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What do closely related species go through during embryonic development?
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Study Notes
Comparative Anatomy
- Study of similarities and differences in anatomy of different species
- Species that share a common ancestor will have some features in common due to their shared ancestry
- Example: forelimb of vertebrates and the similarity in bone structure (pentadactyl limb)
- Homologies: similar structures that are adapted to specific environments but share a common underlying anatomical plan
- Forelimbs of a bat, mole, and dugong: each limb performs a different function but shares similarities in bone structure
Phylogenetic Constraint
- Evolution acts on the body form that is already present and adds variations to it
- Example: we don't see wings and four limbs together; if a species has four limbs, it can be modified with what is already present
Comparative Embryology
- Closely related species go through similar stages of development
- Example: all species have non-functioning gill slits as early embryos; many vertebrate embryos develop a primitive tail
- Evidence for common ancestry and phylogenetic constraint
Vestigial Features
- Structures that have no apparent function and appear to be residual parts from a common ancestor
- Examples: whales' hips and hind legs; snakes' remnants of hindlimbs; humans' appendix
- Evidence for common ancestry
Atavistic Features
- Modification of a biological structure where an ancestral genetic trait reappears after being lost through evolutionary change
- Examples: modern horses' occasional extra toes; reappearance of ancestral traits in later generations
- Evidence for anagenesis and common ancestry
Analogous Features
- Similar features evolved not due to common ancestry but due to similar selection pressures
- Convergent evolution: different species have converged to the same characteristics due to the same selection pressure
- Examples: wings of bats, butterflies, and birds; similar function but evolved independently
Homology and Analogy
- Homology: similar characteristics shared by two different organisms because they are inherited from a common ancestor
- Example: forelimbs of vertebrates (bat wing, mouse forelimb, human arm)
- Analogy: similar characteristics shared by two different organisms because of convergent evolution
- Example: wings of bats, butterflies, and birds (similar function but evolved independently)
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Description
Explore the similarities and differences in anatomy among living species, including the study of vertebrate forelimbs and homologies that provide evidence for evolution.
