Test 1 Comparative embryology

Phylogeny

history of life

Ontogeny

the development of an individual organism from embryo to adult. (history of an individual)

Embryology

A phase of your individual development (it is a portion of ontogeny

Haploid gametes →

syngamy forms zygote

syngamy forms zygote →

cleavage

cleavage →

morula

morula →

blastula

blastula →

gastrula

gastrula →

neurula

neurula →

organogenesis

organogenesis →

birth/hatching

birth/hatching →

growth

growth →

metamorphosis

metamorophosis →

maturation

maturation →

senility

senility →

death

ceolomates (eucoelomates)

tube within a tube (true body cavity)

protostomes

organisms in which the mouth, anus forms secondarily

deuterostomes

Blastopore becomes anus, mouth forms secondarily (second mouth)

Gametogenesis haploid gametes (step 1)

The process of forming gametes through meiosis, involving the development of sperm and eggs from precursor cells. Meiosis results in the reduction of chromosome number, producing haploid cells necessary for sexual reproduction.

Syngamy forms zygote (second step)

The fusion of two gametes, typically involving a sperm and an egg, resulting in the formation of a zygote. This process marks the beginning of fertilization which is external

Cleavage (step 3)

Each stage cuts cells (mitosis) so the number of cells are increasing (they are not growing) it is no longer an egg it is now an embryo

2 types of cleavage

Radial cleavage, spiral cleavage

radial cleavage

occurs in deuterostones results in the formation of a symmetrical arrangement of cells. (cleaved in half) vertebrates are member of this

spiral cleavage

occurs in protostomes and results in a spiral arrangement of cells. (as embryo cleaves it’s spiraling)

Morula (step 4)

A solid ball of cells formed after several rounds of cleavage in early embryonic development. The cells cleave until 32 cells then they start to migrate and rearrange into a blastula.

Blastula (stage 5)

A hollow ball of cells formed after the morula stage, characterized by a fluid-filled cavity the blastocoel (no longer going though cleavage) as it gets large it starts to fold inner

blastocoel

hallow center of the blastula that contains fluid.

gastrula (stage 6)

Stage following the blastula that migration becomes the stomach formation the cells growing inner for the endoderm and the cells on the outside form the ectoderm. As the whole organism grows it elongates the embryo creating a tube within a tube

archenteron

The primitive gut formed during gastrulation that will eventually develop into the digestive tract.

Fate of the blastopore in protostomes (gastrulation)

it becomes the mouth

fate of blastopore in deuterostomes (gastrulation)

it becomes the anus

Origin of mesoderm in protostomes (gastrulation)

it originates from endoderm cells dropping off into blastocoel & proliferating there

origin of mesoderm in deuterostomes (gastrulation)

it originates from outpocketing of the endoderm cells of the archenteron (doesn’t detach but grows outwards)

schizocoel (in protostomes)

cells detach from the mesoderm layer during development, forming a coelom in

Enterocoel (deuterostomes)

the formation of the coelom by the outpocketing of the mesoderm from the archenteron during development.

blastocoel gets replaced with

the coelom during development (goes from hollow space to the coelom)

What 3 germ layers are determined in gastrulation

ectoderm, mesoderm, endoderm

what are the axes of orientation

the vegetative pole and animal pole.

vegetal pole

the region of an egg that contains more yolk and typically develops into the lower part of the embryo. (source of nutrition)

animal pole

the region of an egg that contains less yolk and typically develops into the upper part of the embryo, contributing to structures like the nervous system. (top region of organism)

holoblastic

even cleavage that occurs in animals that do not really have yolk (mammals and smaller animals)

meroblastic

cleavage that is biased happening on one side of the embryo and not on the other(birds, reptiles)

macrolecithal

having a large amount of yolk in the egg, leading to meroblastic cleavage, typically found in birds and reptiles.

teloecithal

yolk is stored on far our reserves relating to macrolecithal eggs

microlecithal

having a small amount of yolk that is evenly distributed

isolecithal

having a small amount of yolk that is evenly distributed throughout the egg, similar to microlecithal eggs, and found in organisms like mammals.

alecithal

lacking yolk entirely, typically found in certain species of mammals.

neurula (stage 7)

comes about during neurulation, it is a cross section through the gastrula stage, and is a long mass of mesoderm above primitive gut

Neurulation

notochord creates a stiffening rod causing the ectoderm to fold in and form the neural tube, which will develop into the central nervous system which is dorsal and hallow because it is folding in.

neural crest cells

migratory cells that arise from the ectoderm during neurulation they are part of the peripheral nervous system

ganglion

a cluster of neuronal cell bodies located in the peripheral nervous system.

the notochord will form

the centra of vertebrae and intervertebral disks

what does the outer layer of primary germ layers contain

Outer skin and nervous system

what does the inner layer of the primary germ layers contain

Gut

What does the ectoderm contain

outer epithelium, nervous system, mouth

what does the central nervous system contain

brain, spinal chord

what does the mesoderm contain

notochord, skeletal muscles, urogenital organs

what does the endoderm contain

gut tube, throat starts endoderm, respiratory track, lining of the urogenital system