Organism Diversity Exam 2
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- What broad characterisics define animals?
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Nutritional Mode
Cell Structure
Cell Specialization
Reproduction and Development - Describe the nutritional mode of animals.
- Chemoheterotrophs with internal digestion (ingestive nutrition)
- Describe the differences of animal cells to other organisms.
- Lack cell walls; held together with structural proteins (collagen) or by junctions (tight, gap)
- What specialized cells define animals?
- Nerve and Muscle cells
- When did animals arise?
- 800 million-1.2 billion years ago
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What fossil assemblages document the origin and early diversification of animals?
(What are they, what period to they cover, and what types of animals are found in each fossil record?) -
Doushantuo Fossils: Pre-Cambrian, microscopic marine organisms
Ediacaran Fossils: Pre-Cambrian, soft-bodied animals
Burgess Shale Fossils: Cambrian, all major phyla - What does Gould mean in his quote: "Three billion years of unicellular, followed by five million years of intense creativity and then capped by more than 500 million years of variation on set anatomical themes?"
- Life began as unicellular and remained that way for the majority of life, then experienced a massive diversification in the Cambrian explosion, and became mere modifications to the original designs, since nearly all phyla were in place.
- What is the Cambrian Explosion and when did it occur?
- Cambrian explosion: the sudden appearance of many different phyla in the geologic record; reflects a sudden dramatic increase in diversity of animals; occured 542-521 million years ago.
- Outline the Ecological, Genetic, and Geological Explanations for why the Cambrian Explosion occured when it did. Are these mutually exculsive or could more than one factor be operating at once?
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Ecological
Resource competition; terrestrial niches empty and waiting to be filled
Predator-prey relationships; natural selection increases
Mass extinctions
Genetic
Evolution of Hox Genes
Mutation
Geological
Climate Change
Atmospheric Change (more available oxygen after plant colonization of land)
NOT MUTUALLY EXCLUSIVE - What are Hox genes? What is their function with respect to body plan development? How do they contribute to the diversification of animal body plans?
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Hox genes: homeobox containing genes regulating development of body segments
Homeobox: 180 bp DNA sequence in genes regulating development; give rise to transcription factors that bind to other genes responsible for development
Location on chromosome determines location of body part - Why don't we continue to see the generation of new animal phyla like we did in the Cambrian Explosion?
- Niches filled; hard for another phyla to evolve when there are no niches available.
- What are choanoflagellates and what is their relationship to animals?
- Phylum Choanoflagella; multicellular protists, closest living relative to animals
- Describe the characteristic early developmental pattern of animals. Do all animals follow this pattern?
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Sperm-egg fertilize; zygote
Zygote cleaves/blastulates; blastula
Blastula gastrulates; gastrula
All animals follow pattern - What is meant by body symmetry, radial symmetry, and bilateral symmetry? How does body symmetry correlate with lifestyle?
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Radial symmetry: animal parts radiate from a central axis; mostly sessile or planktonic animals
Bilateral symmetry; animal parts form two chiral halves; mostly free-living animals - In what ways do the traditional phylogeny of animals based on morphology/embryology and the molecular phylogeny of the animal kingdom agree and disagree?
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Agreements
1. All animals share a common ancestor
2. Sponges are basal animals
3. Eumetazoa is a clade of animals with true tissue
4. Most animals belong to the clade Bilateria
5. Vertebrates and some other phyla belong to the clade Deuterostomia
Disagreement: Relationship among Bilateria
Morphological/embryological cladogram two divisons: protostomes and deuterostomes
Genetic cladogram three: protostomes, ecdysosomes, locotrophozoans - What percentage of animal diversity is composed of invertebrates? What percentage of diversity of life is composed of arthropods
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95% invertebrates
85% arthropods - What is the basic body plan of echinoderms, and how do the various classes within this phylum represent variations on this common body plan?
- Five-point body plan
- What are the four uniting characteristics of chordates? Do humans exhibit these four defining characteristics?
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Notochord
Pharyngel Gill Slits/Clefts
Dorsal Hollow Nerve Chord
Postanal Tail
Humand display characteristics while in developmental stages - What ancestral chordate feature gave rise to the vertebral column? To jaws?
- Vertebral column arises from notochord; jaws arise from modifications to skeletal rods supporting pharyngeal gill slits
- When did primates evolve? What are examples of the most primitive primates today?
- 45 million years ago; Lemurs, Lorises, Pottos, Tarsiers
- What primates constitute the hominoids? How long ago did hominoids arise?
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Constituted by great apes; Giabbons, Orangutans, Gorillas, Chimpanzees, Bonobos, and Humans
Arose about 20-25 million years ago - When did hominids split from the great apes?
- 7-6 million years ago
- What is the closest LIVING relative of Homo sapiens? What is thought to be the CLOSEST RELATIVE of Homo sapiens?
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Living: Chimpanzees (1.2% difference)
Closest relative: Homo Erectus - How can we tell if a fossilized skeleton exhibited bipedlaism?
- Bone structure of pelvis and legs; entrance of vertebral column