STAGES OF DEVELOPMENT

GROWTH

DIFFERENTIATION

MORPHOGENESIS

Cell division and expansion

formation of different cell types of an organism

generation of form or shape of an organism and its organs

1 cotyledons

2 monocot

3 dicot

1 embryonic leaves in the seed

2 one leaf which transfers food from the endosperm to the embryo during germination

3 two leaves, which can absorb the food store or allow it to remain in the seed at maturity.

 development of the zygote

after the zygote begins active cell division to form an organised mass of cells...

1 in angiosperms

2 in gymnosperms

1. the embryo is called a supensor

Cell differentiation begins when there are about 40 cells; and root and shoot have appeared.

the organs and tissues that form a mature pant are formed. Meristems are established early at root and shoot apices

Zygote begins division after fertilisation but no cell walls form between nuclei. after eight sets of division (approx 256 nuclei) the cell walls form and differentiation begins.

angiosperm embryo

long narrow column of cells and a mass of layered cells

for plants, no cell movement, Differentiation occurs in situ where division occurred

Chemical signals do not control plant development once the plant has begun to germinate. The environment influences concentration and distribution of plant hormones directing cell differentiation.

Plant differentiation

undifferentiated

shoot/ root apical meristem---

fully differentiated

Zygote ---- Embryo

Cork cambian, Vascular cambian, Leaf Primordia, Bud Primordia / Cork cambian, vascular cambian, Pericycle, bud primordia

Bark, xylem, phloem, leaves, lateral shoots, shoot elongation /

Bark, xylem, Phloem, lateral roots Tap root.

vascular tissue in vascular plants, e.g. wood.

transports water and some nutrients

Blastula

Blastopore

Gastrula

Zygote undergoes mitotic division to form a hollow ball of cells

blastula folds inwards to form a hollow sac with an opening at one end, which is the begining of the digestive system------forming a gastrula.

Fertilisation

Cleavage

Gastrulation

Organogenesis

the zygote divides into many cells without an increase in size to the zygote

the cells of the zygote move to form three primary cell types/layers, ectoderm mesoderm endoderm

penetration

fusion

cell activation

penetration

acrosome

jelly lsyer

when a sperm comes in contact with an ovum of the same species, receptor protines bind with the outer layer and the acrosome discharges hydrolytic enzymes onto the vitelline layer of the egg.

the acrosomal process allows the acrosome to penetrate this jelly layer

The release of hydrolytic enzymes during the acrosomal reaction leads to fusion of sperm and egg plasma

the cytoplasm of the egg becomes larger and the head of the sperm enters the cytoplasm of the egg. Further fertilisation is prevented by the fast and slow blocks to polyspermy.

With the influx of Ca2+, relative inactivity changes to high metabolic and protien synthesis rate, now that the egg is a zygote

egg activation can be initiated without sperm entrance, this activation forms a polar body which protrudes from the cellular body once division is complete. Second division and second polar body occur once the sperm has entered the egg.

Na+ channels open, the membrane depolarises.

neutraliasation causes Ca2+ channels to open in the egg endoplasmic recticulum

Ca2+ moves across the cell, it causes more water to enter the cell, changing hydrostatic pressure, assisting the acrosomal process and causing the protien receptors (bindin) on the vitelline layer to inactivate, releasing any other sperm.

Cleavage

morula

what causes different outcomes for cells in morula?

blastula

collection of cells (blastomere) resulting from cell division without expansion

each blastomere has a different part of the cytoplasm, which induces a different developemental outcome. 

each blastomere secrets fluid into the centre of the morula, eventually a hollow ball of 500-2000 cells is formed, surrounding a fluid filled cavity, the blastocoel

what is the influence of yolk patterns on cleavage

for

Aquatic Vertabrates

Amphibians

Birds Reptiles

Mammals

Aquatic vertebrate little to no yolk; Holoblastic cleavage results in a symmetrical blastula with cells of approximatly the same size

Amphibians and advanced fish

yolk unevenly distributed. Yolk rich cells divide more slowly, and grow larger, cells without yolk divide quickly and remain small, resulting in a small, dense mass of cells at one end

Reptiles and Birds

eggs are almost entirly yolk, with a blastodisc- small region of cytoplasm in one region- being the only place cleavage occurs - a meroblastic cleavage pattern creating a hollow cap on the yolk.

Mammals - little to no yolk means a holoblastic cleavage. the blastospore forms a small inner cell mass at one end.

The blastula undergoes rearrangement to form the three  primary cell types.

Ectoderm forms skin, central nervous system, sensory organs and neural crest

Mesoderm moves to the interior and forms blood vessels, skeleton, gonads, heart and muscles. The endoderm moves further interior, and forms digestive tract, lungs, and glands.

Vertebrates

development of neural crest