Bio 2 Final

larva

sexually immature, and morphologically and behaviorally distinct from the adult stage

metamorphosis

larvae become juveniles that resemble adults but are sexually immature

Hox genes

genes that regulate the expression of other genes; regulate development

what is the closest living relatives to animals?

choanoflagellates

Cambrian explosion

marks a period of rapid animal diversification

Bilaterians have the following traits…

-bilaterally symmetric form

-complete digestive tract

-efficient digestive system with a mouth and an anus at opposite ends

body plans

sets of morphological and developmental traits

radial symmetry

body parts are arranged around a single central axis

bilateral symmetry

body parts are arranged around two axes of orientation, the head-trail axis and the dorsal-ventral axis

ectoderm

covers the embryo’s surface, and gives rise to the outer covering and central nervous system

endoderm

the innermost layer, lines the blind pouch (archenteron) that will form the gut, and gives rise to the lining of the digestive tract and organs

diploblastic animals

have only ectoderm and endoderm

triploblastic animals

including all bilaterally symmetrical animals, have a third germ layer

mesoderm

fills the space between ectoderm and endoderm, and gives rise to muscles and most organs

body cavity

a fluid-filled or air-filled space between the digestive tract and the outer body wall

coelom

a body cavity surrounds by tissues derived from mesoderm, suspends the internal organs

hemocoel

body cavity formed between the mesoderm and endoderm

spiral cleavage

the planes of cell division are diagonal to the vertical axis of the embryo

determinate cleavage

rigidly determines the developmental fate of each embryonic cell very early

animals with protostome development

have spiral and determinant cleavages

animals with deuterostome development

cleavage is radial and indeterminate

radial cleavage

the planes of division are either parallel or perpendicular to the embryo’s vertical axis

indeterminate cleavage

each cell produced by early cleavage is able to form a complete embryo

archenteron

a blind pouch formed by the embryo during gastrulation; eventually becomes the gut

blastopore

an indentation in the gastrula that leads to the formation of the archenteron

eumetazoans

what group all animals except sponges and a few others belong to

invertebrates

animals that lack a backbone

chordata

the only phylum that also includes vertebrates

members of Deuterostomia

may be invertebrates or vertebrates

all members of ecdysozoa…

secrete an external skeleton (exoskeleton)

filter feeders

captures particles suspended in the water that passes through its body

spongocoel

where water is drawn into

osculum

where water flows out

choanocytes cells in sponges

flagellated collar cells, engulf bacteria and food particles by phagocytosis

mesohyl of sponges

gelatinous region that separates two layers of cells

amoebocytes of sponges

totipotent cells within the mesohyl that digest food, transport nutrients, and make skeletal fibers

hermaphrodites

each individual functions as both male and female

gastrovascular cavity

a sax with a central digestive compartment; a single opening functions as both mouth and anus

polyps body plan

adhere to the substrate by the aboral end of the body (the end opposite to the mouth)

medusa body plan

a free-swimming form that has a bell-shaped body with the mouth on the underside

cnidocytes

unique cells used in defense and prey capture found in the tentacles of cnidarians

nematocysts

specialized organelles within cnidocytes that eject a stinging thread

protonephridia

networks of tubules with ciliated structured called flame bulbs

flame bulbs

pull fluid through branched ducts open to the external environment

alimentary canal

a digestive tube with a separate mouth and anus

parthenogenesis

females produce female offspring from unfertilized eggs

ectoprocts

sessile colonial animals that superficially resemble clumps of moss

branchiopods

superficially resemble clams and other hinge-shaped molluscs

ammonites

shelled cephalopods; once the dominant invertebrate predators of the seas

open circulatory system

uses a heart to pump hemolymph into the cavity surrounding the tissues and organs (the hemocoel)

book lungs

stacked platelike structures responsible for gas exchange in most spiders

four key characteristics of chordates

-notochord

-dorsal, hollow nerve cord

-pharyngeal slits or clefts

-muscular, post-anal tail

notochord

a longitudinal, flexible rod between the digestive tube and nerve cord

pharyngeal clefts

grooves along the outer surface of the pharynx; found in all chordate embryos

pharyngeal slits

allow water to pass from the mouth to the outside of the body, bypassing the digestive tract

neural crest

unique to vertebrates- appears along the edges of the closing neural tube

neural crest function

give rise to many features including teeth, bones/cartilage in the skull, and sensory capsules

lateral line system

rows of organs sensitive to vibrations located along body sides; found in aquatic species

oviparous

eggs hatch outside the mother’s body

ovoviviparous

eggs are retains within the oviduct; young are born after hatching within the uterus

viviparous

young develop within the uterus and are nourished by a yolk sac placenta, absorption of nutrient-rich fluid, or by eating other eggs

cloaca

a common chamber with a single opening to the outside of the body; the reproductive tract, excretory system, and digestive system all empty into it

operculum

bony flaps that protect the gills of fish

amniotes

tetrapods whose living members are the reptiles (including birds) and mammals

amniotic egg

contains found membranes that protect the embryo; reduced the dependence on water for reproduction

amnion

a fluid-filled sac that surrounds, bathes, and cushions the embryo

ectothermic

animals that absorb external heat as the main source of body heat

endothermic

animals capable of maintaining body temperature through metabolic activity

paleoanthropology

the study of human origins