Term
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Definition
asymmetric with no fixed shape
skeleton of spicules
no tissues/organs
cells are not surrounded by membranes
cell differentiation is fully and easily reversible |
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Term
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Definition
suspension feeders
water is drawn in through body pores by movement of choanocyte flagella
nutrients are phagocytosed by choanocytes then passed to amoebocytes for digestion and distribution
many also have algal symbionts to provide fixed carbon |
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Term
| Sponges: defense and attack |
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Definition
produce toxins and have bright warning coloration
spicules make unpalatable
sponges have sponge fights to compete for space
recognition of self; grafting with another species doesn't work |
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Term
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Definition
Asexual reproduction is by fragmentation or external/internal buds made as a hedge against poor growth conditions
sexual reproduction - they are sequential hermaphrodites (no self fertilization) |
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Term
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Definition
a eumetazoan group that diverged early in animal history
radially symmetric and diploblastic with no cephalization
may be polyp, medusa, both or colony |
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Term
| Which cnidarians are most venomous? |
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Definition
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Term
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Definition
There is nerve net, but no nervous centralization or brain
have chemical and mechanical sensors to process information
Some have lenses and retinas
contractile cells for motility |
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Term
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Definition
both a predatory lifestyle and algal symbionts
prey is collected by tentacles around the mouth that are armed with cnidae contained in cells called cnidocytes. An everted thread collects prey, nematocysts can inject painful paralytic toxin |
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Term
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Definition
asexual - by budding
sexual - the larva is small, ciliated planula |
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Term
| Flatworms (Platyhelminthes) |
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Definition
Triploblastic, protostomate and acoelomatous
body is flattened for better gas exchange |
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Term
| Platyhelminthes: Planarians |
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Definition
Usually less than 1cm in length
mainly carnivores
mouth midway down body leading to gastrovascular cavity
have cephalization and rudimentary brain
eyespots for orientation
negatively phototactic and move away from light
asexual reproduction by transverse fission and regeneration
sexual reproduction between hermaphroditic individuals |
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Term
| Platyhelminthes: Tapeworms |
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Definition
all are endoparasitic
nutrients digested by the host pass directly across the body wall of the worm
convert food into eggs and sperm and do little else
can produce 10,000 to 100,000s of fertilized eggs per day |
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Term
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Definition
| segmented worms, some with metameric segmentation (oligochaetes), others with more differentiated segments (polychaetes) |
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Term
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Definition
include earthworms and some freshwater and marine relatives
organ systems are repeated in each segment
locomotion occurs by alternating the contraction of circular and longitudinal muscles
closed circulation
have pseudohearts and contractile vessel walls
deposit feeders - ingest soil, extract nutrients, and leave behind castings
sexual reproduction (simultaneous hermaphroditism) or asexual (fragmentation, parthenogenesis) |
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Term
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Definition
Very large and diverse phylum ~90,000 species
coelomatous and unsegmented
have muscular foot, visceral mass, mantle, and radula
circulation is closed in cephalopods, open in other molluscs |
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Term
| Mollusca: Polyplacophorans |
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Definition
Chitons
grazers in the intertidal region
oval bodies with 8 overlapping dorsal plates
foot for gripping rock, maintaining position or moving slowly
radula for scraping algae off rocks
some have developed eyes made from calcium carbonate |
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Term
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Definition
include snails, nudibranchs, limpets, abalone, conches, periwinkles, whelks, cowries
~60,000 - 75,000 species
80% of all molluscs
only molluscs to become terrestrial
mantle cavity modified to lung
grazers or predators
undergo torsion |
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Term
| What cells in sponges suggest an evolutionary affinity with choanoflagellates? |
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Definition
| choanocytes (collar cells) |
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Term
What are the function of the following molluscan structures?
a) foot
b) mantle cavity
c) mantle
d) radula |
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Definition
a) locomotion, attachment, burrowing
b) location of gills, anus; ,odified to a lung in terrestrial gastropods
c) protection; secretion of calcium carbonate shell
d) scraping food from rocks or drilling the shells of other organisms |
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Term
| How does the arrangement and contraction of muscles in an earthworm generate movement? |
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Definition
| Each segment contains both circular and longitudinal muscles. When the circular muscles contract and the longitudinal muscles relax, the segment lengthens - moves forward. Bristles (chaetae) anchor the segment at the new spot. When the circular muscles relax and the longitudinal muscles contract, the rest of the worm's body is dragged up to the new spot. |
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Term
| What are the functions of the hard arthropod exoskeleton? |
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Definition
| In marine arthropods, muscle anchorage and protection. In terrestrial arthropods, the above two functions, as well as prevention of water loss and support against gravity. |
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Term
| Why are arthropod appendages striking examples of evolutionary homology? |
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Definition
| The arthropod appendage is a very flexible instrument (evolutionarily speaking) that has assumed many different forms and functions: walking, sensing, feeding (mandibles), defense, capture of food, sexual reproduction. Also, different arthropods have different numbers of appendages |
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Term
| Can you set a minimum age for hemoglobin (evolutionarily speaking)? |
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Definition
| Hemoglobin is present in members of Chordata and Annelida. These groups had already diverged by the time of the Burgess Shale formation, late in the period of the Cambrian explosion. Therefore hemoglobin must be at least that old (asssuming that chordate and annelid hemoglobins are homologous molecules) |
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Term
| The bodies of many sponges contain finely branched channels through which water is propelled. What is the advantage of this branching? |
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Definition
| The fine channels are lined with choanocytes, which absorb food particles; the greater the number of choanocytes available for phagocytosis. Also, the water slows down as it branches, giving the choanocytes more opportunity to absorb food particles. |
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Term
| Jellyfish are diploblastic animals, and consequently lack mesoderm and true muscle. And yet jellyfish can move in the water (albeit weakly). How do they do it? |
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Definition
| Jellyfish have elongated contractile cells in the epidermis or gastrodermis that are anchored in the mesoglea. Contractions of these cells distort the body and provide movement. These cells are not considered muscle tissue, however, since the cells are not derived from mesoderm. |
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Term
| Planarians are negatively phototactic. What does this mean, and why is this ability an advantage? |
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Definition
| A negatively phototactic animal can sense light and move away from it. It probably helps the animal hide from visual predators. |
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Term
| Tapeworms do not have a gut or gastrovascular cavity. How do they live without one? |
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Definition
| All members of this group are endoparasitic and are able to absorb, across their body wall, nutrients digested by the host. |
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Term
| The penis fencing contests in which some flatworms engage - contests which sometimes result in the death of one of the combatants - would not appear to be in the best interests of the species. How, then, could such behavior have evolved? |
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Definition
| Behavior, structures and processes that appear by natural selection are not favored by virtue of being good for the species as a whole (whatever that might mean). All that matters is that the genetic variants in question allow their possessor to thrive and reproduce. If the winner of one of these contests produces a lot of offspring as a result, and perhaps lives to inseminate another partner, the aggressive behavior will have selective value. |
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Term
| Suggest a function of chromosome diminution in nematodes. |
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Definition
| One hypothesis is that it may accelerate DNA replication, cell division and therefore development. It is an advantage for a small prey animal to complete its development and reproduce as quickly as possible. |
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Term
| Why is Caenorhabditis elegans a good model for developmental genetics? |
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Definition
| It is small (959 somatic cells); it has a rapid generation time; the lineage of every cell in the adult organism is known. |
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Term
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Definition
| a 180 degree twisting of the visceral mass, due to asymmetric growth and muscle contraction on one side of the embryo |
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Term
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Definition
Includes clams, scallops, mussels, oysters and geoducks
left-right orientation with dorsal hinge
Adductor muscles hold shells together
incurrent siphon to sweep in oxygen and food particles
usually sedentary, often burrowing
scallops are more active |
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Term
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Definition
Octopuses, squids, nautiluses
can eject water forcefully through the siphon to produce rapid, directed movement
are predators with complicated brains and sense organs. They are the most intelligent invertebrates
allows vertical movement in water |
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Term
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Definition
commonly called roundworms
unsegmented and pseudocoelomatous
have complete digestive tract
some forms free-living, others are parasitic on plants and animals
25,000 species known
>500,000 species unknown
all look similar
most individual animals belong to this phylum
embryonic cells go through chromosome diminution
some can undergo cryptobiosis or anhydrobiosis |
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Term
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Definition
one of the best understood animals
model organism for developmental genetics
cell lineages are always the same except when mutated
959 somatic cells
complete lineage is known from zygote to adult
apoptosis - programmed cell death |
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