Animal Reproductive Development Flashcards
What are features that define an animal?
multicellular, heterotrophic eukaryotes that mostly obtain nutrients by ingestion
no cell walls
muscle cells and nerve cells
cell junctions
What are the cell junctions unique to animals?
tight junctions and gap junctions
What are tight junctions?
bind epithelial and endothelial cells tightly together (variety of functions incl. acting as a primary barrier to the diffusion of solutes through intracellular space
What are gap junctions?
channels that physically connect adjacent cells mediating the rapid exchange of small molecules between cells
Describe the life cycle of most animals by sexual reproduction
dominant diploid adult that produces haploid eggs or sperm by meiosis.
gametes fuse to form a diploid zygote
zygote passes through a series of distinct embryonic stages, developing in the adult animal
What are the 4 types of asexual reproduction? which ones do some animals do?
animals:
parthogenesis
budding
fragmentation
not animals;
binary fision
What is Binary fission?
a form of cell division in which the genome replicates and the cell divides into two cells (prokaryotes)
What is budding?
a bud, or protrusion, forms on an organism and eventually brekas off to form a new organism that is smaller than its parent
What is Fragmentation?
new individuals arise by the splitting of one organism into two or more species, each of which develops into a new individual
What is Parthogenesis?
females produce eggs that are not fertilized by males; divide by mitosis and develop into new individuals
What is an example of parthogenesis?
asexual, all-female whiptale lizard (Cnemidophorus neomexicanus)
begisn with a simulated mating ritual in which the females bite and mount each other, so they lay unfertilized eggs, young hatch and are genetic clones of their mothers
What is an example of an animal that can undergo both sexual and asexual reproduction?
Daphnia
What is cleavage (post fertilization step)?
single-celled zygote divides by mitosis - resulting in many smaller cells in a solid ball called a morula
What is the blastula?
later embryonic stage - hollow ball o cells
What is a gastrula?
a saclike embryo with one opening - blastopore - and at least two layers of cells
What are the stages in a embryo development?
zygote, eight-cell stage, blastula, gastrula
What usually happens to the gastrula?
develops into one or more immature stages (e.g. larvae) that later develop into the sexually mature adults after metamorphosis
what is gastrulation?
coordinated set of movement sin which the cells of the blastoderm migrate inward, creating germ layers of cells within the embryo and ancheteron
what is the archenteron?
rudimentary alimentary cavity (‘gut’) of an embryo at the gastrula stage
what are germ layers?
primary layers tha forms during embryonic development
What is the ectoderm?
surface of the embryo forms the nervous system and outer surfaces such as skin, pigment cells and hair cells
What are the two types of germ layer?
ectoderm and endoderm
What is the endoderm?
inner most germ later, forms the respiratory and digestive tracts, as well as associated organs such as the liver and pancreas
how many germ layers do most animals have? called?
3 (bilaterians) called triploblastic
How many germ layers do cnidarians have? called?
2 called diploblastic
What is the mesoderm?
germ layer between the ectoderm and the endoderm forms majority of body organs, including muscle =, blood vessels, kidney, heart and skeleton
What are homeobox genes?
a group of genes that are involved in the regulation of patterns of anatomical embryonic development in multicellular organisms
What are hox genes?
special regulatory homeobox genes which control zygote development along the anterior-posterior axis
When do fossils of the oldest animals date from?
Proterzoic eon roughly 550-600 million years ago
What are the origins of Ediacaran fauna?
from Ediacara Hills Australia
What is the Cambrian explosion?
‘modern’ animal body plans evolved during period of rapid diversification between 542-488 million years ago
What preserved biotas allow for the base of diversity explosion in the Cambrian period?
Burgess Shale and Chengjiang
What is the sister clade for animals?
Choanoflagellates
What are choanoflagellates?
free-living, single-celled and colony forming eukaryotes ubiquitous in aquatic environments (marine and freshwater)
What do choanoflagellates cells resemble that are found in sponges?
specialised cells called choanocytes that line the canals of sponges
What supports the relationship of choanoflagellates to sponges?
molecular and morphological data
mitochondrial genome sequences confirm placement as outgroup to multicellular animals (metazoa) and negate reverse
What are metazoa?
multicellular animals; animals with differentiated tissues (all animals except sponges) are eumetazoans
What is a body plan?
a group of animals that share the same morphological and developmental traits
What is radial symmetry?
a circular body plan having a central axis from which structures radiate outward
What is bilateral symmetry?
a body plan in which the right and left sides of the body are mirror images of each other
What is cephalization?
animals with bilateral symmetry exhibit the evolutionary trend of concentrating nervous tissue and sense organs toward the anterior of animals
What is the nervous system like in Cnidarians?
nerve cells form a decentralized nerve net
What is nervous system like in planarians? and those that exhibit bilateral symmetry
neurons cluster into an anterior ganglion that process information
What is nervous system like in arthropods?
a brain - and clusters of nerve cell bodies, called peripheral ganglia, located along the ventral cord
What is nervous system like in Mollusks? e.g. squid and octopi
must hunt to survive have complex brains with millions of neurons
What is nervous system like in vertebrates?
brain and spinal cord comprise the central nervous system, while neurons extending into the rest of the body comprise the peripheral nervous system
Which animal does not have true tissues?
sponges (two layers of cells but no distinct tissues despite differentiated cell types (called parazoans)
What is the embryo like in Cnidarians? e.g. jellyfish … Bilaterians?
have embryos with 2 germ layers ecto and endoderm. (diploblastic) (bilaterians are triploblastic)
What is a body cavity? formed?
(or coelom) is a fluid filled sac separating the gur from the outer body wall
among bilaterians (3 germ layers) further development of the embryo may result in its formation.
what are the three groups based on body cavity presence?
acoelomates, pseudocoelomates, and eucoelomates
What are acoelomates?
no body cavity between the gut (endoderm) and the outer body wall (ectoderm)
What are Pseudocoelomates?
fluid filled body cavity that is not completely lined with mesodermal tissue
What are Eucelomates?
fluid filled body cavity that is completely lined with tissue that is derived from the mesoderm
WHat is the distinguishin g difference between Protostomes and Deuterostomes?
mouth forms from blastopore in Protostomes
and anus forms from blastopore in Deuterostomes
What is the cleavage in Protostomes like?
Spiral determinate development - divisions after the third cleavage are unequal; eight cell stage creates 4 larger cells and 4 smaller cells
WHat ius cleavage like in Deuterostomes?
Radial indeterminate development - division after the third cleavage equal
What is Spiral cleavage?
cells cleavage is diagonal or off-set to vertical axis cleavage of lower tier cells
WHat is Radial cleavage?
upper tier cells cleavage is parallel or directly over axis of lower tier cells
What does determinate mean?
the developmental fate of each cell is predetermined at the early embryonic stage
What does Indeterminate mean?
the cells of the eight-cell embryo, if separated, remain capable of developing as complete organisms
What is the difference in coelom (body cavity) formation for protostomes and deuterostomes?
protostomes is schizocoelous development; coelom begins as splits within the solid mesodermal mass
Deuterostomes is enterocoelous development; mesoderm arises as lateral out pockets of the archenteron that develop into coelomic cavities
What are the two ways animal phylogenies have been created?
by body plans and by molecular sequence data
What are the points of agreement between both phylogenetic trees?
all animals share a common ancestor
sponges are basal animals
eumetazoa is a clade of animals with true tissues
most animal phyla are members of the Bilateria clade
Vertebrates and other phyla consistently belong to the Deuterstomia clade
What is the challenge of sponges being basal animals?
ctenophores are basal instead
What are the points of disagreement between the 2 phylogenetic trees?
morphologically (body plan) based tree has bilaterians as two clades and molecular has 3
WHat are the 3 clades in molecular based tree?
Deuterostomes and 2 protostomes: ecdysozoans and lophotrocozoans
What are Ecdyzoans?
undergo ecdysis (molting)
What are Lophotrochozoans?
presence of a lophophore or a trochophore larva
