Midterm #1

Question 1

Epibenthic

Answer 1

: Living on or just above the substrate

Question 2

Infaunal

Answer 2

Living within the substrate

Question 3

Pelagic

Answer 3

Organisms live within the water column

Question 4

Apomorphy

Answer 4

any derived or specialized character

Question 5

Autoapomorphy

Answer 5

a derived character possessed by only one descendant of an ancestor, and thus of no use in discerning relationships among other descendants

Question 6

Cladogenesis

Answer 6

the splitting of a single lineage into two or more distinct lineages

Question 7

Homoplasy

Answer 7

the independent acquisition of similar characteristics (character states) from different ancestors through convergence or parallelism. Such homoplastic events create the illusion of homology.

Question 8

Paraphyletic Grouping

Answer 8

a group of species sharing an immediate ancestor but not including all descendants of that ancestor.

Question 9

Pleisiomorphy

Answer 9

any ancestral or primitive character

Question 10

Polarity

Answer 10

The direction of evolutionary change

Question 11

Polyphyletic Grouping

Answer 11

an incorrect grouping containing species that descended from two or more different ancestors. Members of polyphyletic groups do not all share the same immediate ancestor. Members of polyphyletic groups may resemble each other because of the independent evolution of similar traits by different ancestors

Question 12

Saturation

Answer 12

a situation in which the gene sequences being compared have experienced so many base-pair substitutions hat the phylogenetic signal is largely lost.

Question 13

Synapomorphy

Answer 13

a derived character that is shared by the most recent common ancestor and by two or more descendants of that ancestor. In cladistic methodology, synapomorphies define clades; that is, they determine which species (or other groups) are most closely related to each other. Essentially, synapomorphies are homologous characters that define clades.

Question 14

Cladistics

Answer 14

Cladistics is an approach to biological classification in which organisms are categorized in groups based on hypotheses of most recent common ancestry

Question 15

Phylogenetic Classification

Answer 15

is the evolutionary history of group of related organisms

Question 16

Choanoderm

Answer 16

Internal cell layer of sponge. Made of choanocytes

Question 17

Pinacoderm

Answer 17

External cell layer of sponge. Made up of pinacocytes

Question 18

Mesohyl

Answer 18

Gelatinous middle (connective) layer in a sponge. Made of spicules, collagen and archaeocytes

Question 19

Choanocyte

Answer 19

Flagellated collar cell responsible for current and food capture

Question 20

Archaeocytes

Answer 20

free ameboid cells; food digestion, nutrient storage, skeletal secretion and gamete differentiation

Question 21

Spicules

Answer 21

Structural components of the sponge. Calcium or silica

Question 22

Spongin

Answer 22

the modified type of collagen that forms the mortar to help hold together spicules

Question 23

Choanoflagellates

Answer 23

the clade of unicellular heterotrophs

Question 24

Asconoid

Answer 24

Basic body plan, atrium with a single osculum

Question 25

Syconoid

Answer 25

Infolding of the atrium to form radial canals. More complex with increased SA

Question 26

Leuconoid

Answer 26

Highly complex body plan, with many, flagellated chambers and often many oscula

Question 27

Class Calcarea

Answer 27

calcareous spicules and all 3 body plans

Question 28

Class Demospongiae

Answer 28

Siliceous spicules and/or spongin. Leuconoid and most sponges belong to this class

Question 29

Class Hexactinellida

Answer 29

Siliceous spicules (6 point fusion) and syncytial tissue

Question 30

Syncytial Tissue

Answer 30

Multinucleate cell with cytoplasmic mass confined within one cell membrane

Question 31

Gemmules

Answer 31

a tough-coated cluster of dormant embryonic cells produced by freshwater sponge. Wait for favourable conditions then develop (asexual)

Question 32

Cnidaria Major Characteristics (6)

Answer 32

True Gut (carnivores)
Diploblastic
Radial Symmetry
Nerve Net
Cnidocytes – synthesize cnidae 
Alternation of generations: polyp and medusa