21.1: Fundamental mechanisms of development

Embryogenesis

The development of a multicellular organism from a zygote.

Cell potency

A cell's potential to differentiate into another cell

Morphogenesis

Process by which cells and tissues organize and arrange themselves to create the final form of the body.

House-keeping genes

Genes expressed in all cells - involved in fundamental biological processes

Cell specific genes

Genes that determine a cell's distinct morphology function and behaviour - expressed in some cells.

Differential gene expression

Some genes are expressed in one cell type but not another

Meristems

Allows plants to have flexible body plans with continual addition of new organs and tissues in form of modules = indeterminate body pattern of growth.

Darwin

Proposed evolution - nature does not take leaps meaning large changes like suddenly developing wings would not happen

Richard Goldschmidt

Hypothesized that small DNA changes could result in big changes which he called hopeful monsters

morphogenesis processes

• division

• changing shape (expansion)

• moving (not seen in plant embryogenesis)

• adhering to one another (not in plant embryogenesis)

• death

commonalities of animal and plant development

• division of zygote to produce many cells

• cells become determined to take on certain fates in different parts of embryo

• cells differentiate accordingly

differences between animal and plant development

• plants = division more precisely orientated and sedate vs. more random in animals

• plant cells expand in size vs. animal cells expand and change shape

• no cell movement in plant vs. animals can move and form coherent tissue

• plants have apical-basal orientation vs. animals have anterior-posterior body plan

plant morphogenesis associated with

orientated cell divisions and expansion

animal morphogenesis associated with

more random cell divisions, cell shape changes, cell movement and adhesion to form tissue and de-adhesion

apical-basal orientation

the organization of plant structures along a vertical axis from the shoot (apical) to the root (basal)

anterior-posterior axis

the organization of body structures along a horizontal axis from the head (anterior) to the tail (posterior).

post-embryonic growth patterns in animals vs plants

animals = during embryogenesis all organ and tissue types are formed = after birth only increase in size until adulthood = determinate growth

plants = few organ and tissue formed in embryogenesis = continuously generate new organs and tissues following emergence from seed due to meristems = indeterminate growth