Animal Development Lecture Flashcards
Strictly vocab and lecture material
Zoology definition
Study of living things
All animals have these features (7)
Eukaryotic,
multi-cellular,
heterotrophic,
mobility,
sensory/nervous system,
extracellular matrix,
cell-cell signaling
Most common method of discovering ancestry now
Gene sequencing
Emergent properties
Descendants having new properties their ancestors did not
Indirect vs Direct development (2)
Indirect: Having a larval stage that undergoes metamorphosis to become an adult
Direct: Being born as a small adult that then grows larger without metamorphosis
Gamete vs Zygote ploidy
Haploid and Diploid, respectively
Spermatogenesis - What process is it? Yields? (6)
Production and maturation of sperm in the testis. It is
1 Spermatogonium –>
1 Primary spermatocyte –>
2 Secondary Spermatocyte –>
4 Spermatids –>
4 haploid spermatozoa
Meiosis
Making 4 haploid reproductive cells from 1 diploid spermatocyte or oocyte that are varied genetically, introducing genetic variability into the zygote.
Oogenesis (7)
Production and maturation of ova in the ovary.
Cytoplasm is favored in the ovum and unfavored in the 3 polar bodies.
Genetic partitioning is still equal amongst the polar bodies and ovum.
Oogonium –>
Primary oocyte –>
secondary oocyte + polar body –>
ovum + 3 polar bodies.
Function of forming a zygote (4)
Restoration of diploid # chromosomes,
Recombination of maternal and paternal genes,
activates the egg to begin development,
sperm contributes a centriole
Fertilization initial process (6)
Sperm comes near the surface of the ovum.
The acrosome of the sperm releases digestive enzymes.
The acrosome and ovum membranes fuse.
The sperm enters the ovum’s membrane.
Nuclei fuse to become a diploid zygote.
Blocks to polyspermy occur.
Polyspermy and why is it bad? (2)
When more than one sperm penetrates the egg during fertilization.
Polyspermy is bad because excess male genetic material complicates embryonic development and results in death of the zygote.
Slow block to polyspermy
The space between the vitelline envelope and plasma membrane of the egg fill with a hard substance, forming a mechanical barrier that prevents sperm from entering the egg. This forms the fertilization membrane.
Fast block to polyspermy
Change in electric potential energy of the plasma membrane is done within a few seconds after the first sperm binds to the nucleus of the egg. This shifts from a negative to a positive charge. Sperm cannot fuse to membranes with a positive charge, so polyspermy is avoided this way.
Embryonic cells are called (cells that have been cleaved)
Blastomeres
Cleavage pattern depends on
How much yolk is present, phylogeny (genetics)
Isolecithal, Mesolecithal, Telolecithal eggs
Small amount of yolk that is evenly distributed,
moderate amount of yolk that is concentrated at the vegetal pole,
large amount of yolk, concentrated at the vegetal pole
A-V axis
Animal pole is north, Vegetal pole is south
Holoblastic cleavage
Cleavage that occurs through the entire egg, occurs in iso/mesolecithal eggs
Yolk - consequences of yolk?
A substance that nourishes the embryo but impedes cleavage, leading to cleavage being slowed down or not occurring at all. As cleavage continues, the site where there is no yolk will be cleaved at a far greater rate than the yolky side of the egg, leading to that portion of the egg having more blastomeres. Gastrulation can occur around the mass of vegetal yolk that remains uncleaved. This occurs in frogs.
Meroblastic cleavage
Occurs in telolecithal eggs (think chicken eggs), all cleavage occurs at the animal pole of the egg and the yolk remains undivided. This can evolve independently in deuterostomes and protostomes
Telolecithal eggs will produce young that …
Hatch at a later developmental stage
Three main differences between mitosis and meiosis
ploidy of product (diploid vs haploid),
somatic vs reproductive cell development,
Clone of parent cell vs Genetically variant relative to parent cell
Direct development occurs because the egg…
Has lots of yolk, young that hatch a later developmental stage
Spiral vs Radial cleavage
perpendicular/parallel is radial, oblique (45 degrees to A-V axis) is spiral
Consequence of spiral cleavage
Cells are divided unequally at an oblique angle, leading blastomeres to have differences in cytoplasm
Alternative means of providing nutrients to developing young?
The placenta provides nutrients to the developing young
Rotational cleavage
An evolution of radial cleavage where there is holoblastic radial cleavage occurring; however, the cleavages are occurring perpendicular relative to each other.
Blastula
End of cleavage produces a blastula with a blastocoel cavity
Blastocoel
The inner cavity of the blastula/gastrula
Gastrula is formed by… and is…
Gastrulation, where the blastopore invaginates the gastrula and forms the archenteron.
Formation of the mesoderm and coelom occur as well.
Blastopore
First hole of the gastrula
Archenteron
Deep to the blastopore, which becomes the gut
Mesoderm (3)
Formed by enterocoely or schizocoely.
Becomes the muscles, reproductive organs, peritoneum (lining of coelem), skeleton
Complete gut
Where the archenteron goes clear to the other side, forming a single gut tube.
Ectoderm
outer layer of cells of the gastrula,
becomes surface of the body epithelial tissue and nervous system
Endoderm
inner layer of cells of the gastrula -
forms epithelial tissue lining of the gut tube
Germ layer
Two or three basic layers that give rise to the various organs and tissues that arise in the multicellular animal
Diploblastic vs Triploblastic
Ectoderm/endoderm formation vs Ectoderm/endoderm & mesoderm formation
4 traits of protostome
Spiral cleavage, Schizocoely, Mosaic embryo, Blastopore becomes the mouth, anus forms secondarily
4 traits of deuterostome
Radial cleavage, enterocoely, regulative embryo, blastopore becomes the anus, mouth forms secondarily
Why are sponges unique?
They do not gastrulate, so they do not have germ layers.
Schizocoely
Mesoderm cells arise from the lip of the gastrula to the mesodermal site then rapidly divide to form the mesoderm.
Enterocoely
Archenteron cells form a mesodermal pouch while the ectoderm gives this process space, and the mesodermal pouches pinch off into a mesoderm with a coelom.
Coelom (2)
Deep to the mesoderm,
forms the body cavity
Are coeloms different between Schizocoely and Enterocoely?
No, they are functionally identical. The way they are formed is an inherited and explains evolutionary relationships.
Regulative vs Mosaic development
Regulative blastomeres can be broken apart and evolve independently.
Regulative relies on interactions with neighboring cells.
Mosaic blastomeres require all blastomeres to participate in development of the embryo or the development will be terminated.
