Study questions for this week's animal lectures....
1. What similarities exist among all animals?
They are multicellular heterotrophs with internal digestion, and they all develop through zygote, morula, blastula, and gastrula stages.
2. Draw the steps on animal embrylogical development.
Zygote (one cell), morula (solid ball of cells), blastula (hollow ball of cells), gastrula (infolded ball with an outer and inner cell layer, a digestive cavity with one opening to the environment)
3. Draw a phylogeny of animal phyla. Include the following groups (Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Mollusca, Chordata, Echinodermata, Crustacea, Hexapoda) and distinguish them based upon these characteristics: body symmetry; number of embryological tissue layers; fate of the blastopore; pattern of growth (adding segments or shedding).
4. Describe the function of the three cell types in sponges.
Choanocytes - filter water and absorb organic food particles
Ameobocytes - absorb food from choanocytes and transport it to porocytes
Epidermal cells - protection on out side of animal
5. How are cnidarians and sponges similar in body plan?
Two layers
Central digestive cavity - absorb food by phagocytosis
6. How do cnidarians feed and digest? What two body plans are exhibited by Cnidarians? Name three groups of Cnidarians.
They are predators that sting their prey and then move it into the digestive cavity. There is both extracellular and interacellular digestion. Cnidarians occur as polyps and medusa. Groups are Anemones, Corals, Hydras, and Jellyfish
7. Distinguish between protostomes and deuterostomes.
The blastopore becomes the mouth in Protostomes, and the blastopore becomes the anus in Deuterostomes.
8. How is bilateral symmetry related to cephalization?
The evolution of a body plan with two sides also creates a front and back and top and bottom. The existence of a "front" favors the concentration of sensory systems at that end of the animal. This concentration of sensory systems is 'cephalization', or formation of a head.
9. Distinguish between the two major divisions of protostomes.
The Lophotrochozoans grow by adding segments, while the Ecdysozoans grow by shedding a cuticle (or exoskeleton).
10. How are nutrients distrubuted from the planarian gut to the rest of the tissue?
The gastrovascular cavity has 'outpocketings' that radiate out into deep tissue, bringing food directly to most cells.
11. What evidence is there in Platyhelminthes of an association between bilaterality and cephalization? Why is this adaptive? (Why is a head a good thing?)
This most primitive group of bilaterally symmetrical animals has anterior ganglia (brains), anterior eyespots, and anterior auricles (for detecting chemicals). So, the concentration of sensory systems at the anterior end of the organism (head) correlates with bilaterality. A head is a good thing because you can monitor the environment for food or danger as you approach it (and before you are IN it!!)
12. List three Platyhelminths
Planaria, Tapeworm, Fluke
13. What is the major innovation of the Lophophorates?
A complete digestive tract is a big one... this allows for specialization of function along the tract, and food now always moves one way (rather than being all mixed up in a gastrovascular sac).
14. The Annelids are segmented. Why is segmentation an important evolutionary innovation?
Sementation is the duplication of entire body regions... and like gene duplication, this allows one 'copy' to specialize for one function while the other maintains the original function (or specializes for something else...)
15. List three types of Annelids.
Earthworms, Polychaetes, and Leeches
16. Consider bivalves and cephalopods and describe how their body plan is modiied from the ancestral "chiton-like" ancestor. Relate these differences to their ecology.
Bivalves have 'lost their head'... they are decephalized, and some even have distributed the sensory system throughout the animal (scallops have eyes all along the edge of the mantle). This correlates with their sedentary lifestyle. They don't move through the environment, so there is no priority of having the sensory systems 'up front'. In fact, as sedentary animals, it's adaptive to disperse the sensory system so you can monitor the environment in every direction and see what's sneaking up on you.
Cephalopods have evolved along the opposite extreme. They are mobile, agile predators. Their mantle has become modified into a hydrodynamic 'dart' that can shoot through the water, and the muscular foot has evolved into a subdivided grasping tool to subdue prey. Their extreme cephalization correlates with their mobility and ecological role as active prdator...
17. Describe the morphological transitions from the Nematodes to the onchyphorans to the arthropod groups.
Nematodes - unsegmented
Onychophorans - segmented, with segmented legs
Arthropoda - segmented, but with specialized body regions
18. List the four phyla of arthropods.
Crustacea
Chelicerata
Myriapoda
Hexapoda
19. For EACH of the these existing arthropod groups (the crustaceans, chelicerates, and hexapods). describe the pattern of segmentation - specialization - reduction that occurs.
Crustaceans show the entire continuum the best...: from the remipedia (unspecialized) we have shrimp, then lbsters, then crabs.... these last three show specialization and progressive reduction of the abdomen...
Chelicerata: from scorpions with specialized segments we see reduction of the head and thorax in the spiders and mite/ticks.
Hexapoda: from collembolans that are rather unspecialized, we move to insects with fusion of body regions and specialization of body regions.
20. What are two characteristics of Echinoderms?
Endoskeleton
water vascular system
21. List the four characteristics of the Chordates.
Hollow dorsal nerve tube
notochord
pharyngeal gill slits
post-anal tail
22. How do the Chordate subphyla differ?
Urochordates are sedentary filter feeders and notochord is posterior.
Cephalochordates are mobile or sedentary filter feeders and the notochord is anterior
Vertebrates are mobile and have cartilaginous or bony vertebrae
23. How did jaws evolve, and why was this adaptive?
Jaws evolved from gill supports (arches). This allowed the vertebrates to enter the role of predator, rather than simply detritivores or parasites
24. What is a swim bladder and why is that adaptive?
A swim bladder is an internal bouyancy organ that evolved from the primitive lung of fish. It is adaptive because the fish can now maintain position in the water column without expending energy by swimming to stay in place.
25. What is one scenario for why fish moved onto land and evolved inot amphibians? What were the benefits of a terrestrial existence for these vertebrates?
The warm swamps of the Devonian were probably low in oxygen. Gulping air at the surface and the evolution of limbs to move in shallow water produced the adaptations needed to move onto land... probably adaptive because these vertebrates could 1) take advantage of the arthropods that had already colonized and 2) escape their own predators, and 3) have more oxygen.
26. What adaptations do reptiles have that allows them to colonize dry habitats?
Scales, a shelled egg, and a nitrogenous waste that does not require much water for excretion.
27. How do bird lungs work, and why do birds have this adaptation?
The one-way lung of birds allows air to move through the respiratory cavity in one direction.... so even on an exhalation, some new air is moving into the lung... a one-way transport is more efficient that a sac (think digestion, too - a one-way gut is more efficient at extracting energy than a digestive sac...). Birds fly, and this demands the most energy of any vertebrate activity... so it is understandable why birds alone have evolve this method of increased aerobic efficiency. You don't want to go anaerobic when you are 500 feet off the ground...
28. What are the three types of mammals? What is the benefit of marsupiality over egg-laying? What is the benefit of placental reproduction over marupiality?
Monotremes - lay eggs; produce milk from glands on the belly, but no nipples to regulate flow.
Marsupials - give birth to an embryo that attaches to a nipple and is carried with the female until it completes development. The embryo is always with the adult and is protected.
Placentals - the transfer of food directly through the placenta is more energetically efficient than converting it to milk and then losing more energy through the digestion process. So, development is more rapid. Also, this allows for 'precocious' offspring that are behaviorially independent (can stand and run) immediately after birth. This increases juvenile survival.
29. Place these hominids in the correct order: A. africanus, A. afarensis, H. sapiens, H. erectus, and H. habilis
A. afarensis... A. africanus.... H. habilis...H. erectus....H. sapiens
30. Explain this conundrum.... how come chimps are more genetically similar to humans, but more morphologically and behaviorally similar to gorillas?
The small amount of genetic change that distinguishes humans from chimps must have a large effect.
31. Some suggest that a small change in developmental genes could be responsible for the morphological and behavioral differences between humans and other apes. Explain, using evidence.
Small changes in the timing of developmental events can have a dramatic effect on the final product. So, if the small genetic changes alluded to in question 30 were in developmental genes, the morphological and behavioral effects could be dramatic. The evidence for this would be that the morphological and behavior differences among these species would correlate with developmental differences. this is indeed the case. As primates develop, the head/body ratio declines, the limb/body ratio increases, the amount of hair increases, the jaw/head ratio increases, and behavioral flexibility declines. These are all similar to the major morphological differences between humans and apes - humans retain the juvenile characteristics (large Head/body ratio, short limb/body ratio, less hair, smaller jaw, and the capcity for learning).