Ch 32 Introduction to Animal Evolution Flashcards
Characteristics of animals
1) Multicellular eukaryotes
2) Heterotrophs
3) Cells lack cell walls
4) Bodies held together by structural proteins (collagen)
Collagen comprises much of what?
The fibers in connective tissues
What is the most abundant protein in the bodies of animals?
Collagen
How do most animals reproduce?
Sexually
Cleavage
Rapid cell division of the zygote
What tissues are unique, defining characteristics of animals?
1) Muscle tissue
2) Nervous tissue
Tissue
Groups of cells that have a common structure, function, or both
How do animal body plans vary?
According to the organization of the animal’s tissues
During development, what gives rise to the tissues and organs of the animal embryo?
Germ layers
Blastula
Formed by cell cleavage
Ectoderm
The germ layer covering the embryo’s surface
Endoderm
The innermost germ layer
The endoderm lines what?
The archenteron
Archenteron
Developing digestive tube
Diploblastic animals
Possess an ectoderm and endoderm
Three diploblastic animals
1) Corals
2) Jellyfish
3) Comb jellies
Triploblastic animals
Posses an ectoderm, mesoderm, and endoderm
Bilaterian
Possess bilateral symmetry
Cephalization
Organization of senses and locomotion toward a head region
All multicellular animals posses what kind of symmetry?
Bilateral symmetry
Larva
Sexually immature and anatomically distinct from the adult
Juvenile
Resembles an adult, but is not sexually mature
Animal diversity arose from what?
A hypothesized ancestor
How long ago did the hypothesized ancestor of animals live?
Between 675 and 800 mya
The hypothesized ancestor of animals resemble what?
Modern choanoflagellates
Choanoflagellates
Protists that are the closest living relatives of animals
Cambrian explosion
Marks the earliest fossil appearance of many major groups (phyla) of living animals
How long ago was the Cambrian explosion?
535 to 525 mya
Three main hypotheses regarding the cause of the Cambrian explosion:
1) New predator-prey relationships
2) A rise in atmospheric oxygen
3) The evolution of the Hox gene complex
What organisms posses Hox genes?
Most animals, and only animals
Hog genes
Regulate many other genes and control the development of body form
Despite being highly conserved, the Hox family of genes produces what?
A wide variety of animal morphologies
Most species are what?
Arthropods
How many species of arthropods are there?
Over one million
How many of all known animals of arthropods?
About 3/4
Protosome cell proliferation
Cell proliferation following fertilization is by spiral cleavage
Deuterostome cell proliferation
Cell proliferation following fertilization is by radial cleavage
Protostome coelom development
Coelom forms within the middle tissue germ layer
Deuterostome coelom development
Coelom forms from outpocketing of the middle tissue germ layer
Protostome initial opening
Initial opening into the gut becomes the mouth
Deuterostom initial opening
Initial opening into the gut becomes the anus
What distinguishes protostomes and deuterostomes?
Embryonic development
Coelom
The body cavity surrounding the gut
What was previously the basis for major classification within the protostomes?
Coelom
Protostome groups previously based on coelom have been shown to be what?
Polyphyletic
Phylum Placozoa
Possibly the simplest animals with the smallest genome
How many genes are possessed within the genome of placozoans?
11,500 genes
How many cell types are possessed by placozoans?
Only four cell types
Phylum Placozoa lack what?
1) Symmetry
2) Organs
3) Muscles
4) Nervous system
