Some cells in the colony may specialize for different tasks
cleavage
the first few divisions of a zygote
-Cleavage patterns distinguish animal groups:
radial cleavage
cells divide completely and evenly (ancestral)
spiral cleavage
complex division (derived)
gastrulation
a series of cell and tissue movements in which the blastula-stage embryo folds inward, producing a
gastrula.
gastrula
an embryo at the stage following the blastula, when it is a hollow cup-shaped structure with an indent
called a blastopore
diploblastic
animals have 2 cell layers (ectoderm and endoderm)
triploblastic
animals have 3 cell layers (ectoderm, mesoderm, and endoderm)
what are the 2 ways triploblastic animals can develop?
,protostomes and deuterostomes
protostome
the blastopore becomes the mouth ("mouth first")
deuterostome
he blastopore becomes the anus ("mouth second")
What are the 3 possible kinds of symmetry an animal can have if not asymmetrical?
spherical symmetry, radial symmetry, and bilateral symmetry
spherical symmetry
A body form in which any cut through the organism's center results in identical halves
radial symmetry
Symmetry about a central axis.
bilateral symmetry
arrangement of body parts so there are distinct left and right halves that mirror each other
cephalization
concentration of sensory and nervous tissue at the head-end (bilaterally symmetrical animals only)
What are the 3 types of body cavities an animal can have?
acoelomate, pseudocoelomate, and coelomate
Acoelomate
-No fluid filled body cavity
-Space between gut and body wall is filled with cells called mesenchyme
-Movement by cilia
pseudocoelomate
-Body cavity is a pseudocoel: a fluid-filled space where organs are suspended
-Muscles only on the outside
coelomate
-Coelom develops within mesoderm
-Lined with a layer of tissue that also covers organs
-More control over movement of fluids within body cavity
Body cavities can act as hydrostatic skeletons, what does this mean?
, When muscles contract they push fluid to another part of the cavity, which causes that region to expand
(locomotion for earthworms)
-An animal with circular and longitudinal muscles can have even greater control over movement
What is the purpose of segmentation?
-Facilitates specialization of body regions
-Allows animal to alter body shape and control movements precisely
which groups of animals have jointed limbs?
arthropods and vertabrets
What are the types of nervous systems an animal can have?
none, diffuse nervous system, or central nervous system
diffuse nervous system
nerve cells are distributed throughout the organism, usually beneath the outer epidermal layer. Large
concentrations of nerve cells—as in the brain—are not found in these systems, though there may be
ganglia, or small local concentrations of neurons.
central nervous system
Made up of a brain and spinal cord
-Coordinates muscle action and movement
-Processes sensory information
-Light, sound, movement, touch,electrical fields, chemical signals Learning
endoparasites
live inside host, often have no digestive system (absorb nutrients through diffusion)
ectoparasites
live on the outside of host, often have mouth parts to pierce or suck out host fluid
detritivores
-Feed on decomposing organic matter(detritus)
-Important ecosystem function by returning nutrients to the environment
direct development
babies very similar to adults
indirect development
babies differ dramatically from adults
what is metamorphosis?
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