Exam 4 Flashcards
tissue
groups similar cells that act as a functional unit
Blastula
- hollow sphere of cells
- water balloon
Gastrula
the cells start making a pooch inside (infolding)
endoderm
inside layer forms lining of digestive tract
ectoderm
outer cell layer forms skin and nervous system not folded
mesoderm
middle cell layer give rise to muscle and most internal organs
Larva
sexually immature individual that look different from the adult animal
metamorphosis
larva undergoes major change in body form and becomes a mature adult
homeotic genes (HOX genes)
- master control genes
- set of genes that decide what other genes get turned on or turned off
Cambrian explosion
few to many kinds of animals
Why did the Cambrian explosion happen?
- increase of atmospheric oxygen
- arrival of homeotic genes
- increasingly complex predator-prey relationships
- all the animal phyla today can be traced back to this period
irregular symmetry
no symmetry
Radial symmetry
animals that can be divided among many planes and still be the same
Bilateral symmetry
- having only two sides
- can be split in half and get a mirror image
- triploblastic animals
Body Plan
- set of morphological and developmental traits
- what it looks like and maybe how it develops
no tissue layers
- no true tissues
- sponges
eumetazoans
Organisms with tissues (at least two layers of tissues)
diploblastic
two layers of tissue; have ectoderm and endoderm (inside and outside)
Triploblastic
three layers of tissue; include mesoderm
coelom
- Body cavity
- fluid filled space between digestive tact and outer body wall
- cushions organs
- allows organs to grow and move independently of body wall
hydrostatic skeleton
soft bodied animals, fluid in the body cavity used to their advantage
- usually for movement
acoelomates
Triploblastic animals that lack a body cavity
Coelomates
- have a true coelom
- true cavities are developed in the mesoderm (embedded in)
Pseudocoelomates
fake cavity are developed next to the mesoderm