Understanding Embryonic Development and Plant Reproduction

What Is Embryonic Development?

Embryonic development includes the processes from the formation of the zygote to the birth of the new individual. After fertilization, the zygote undergoes many cellular changes and becomes a developing organism, called an embryo. Depending on the species, embryonic development takes place in three main ways:

Viviparous Development

• The embryo develops inside the female body where it receives nourishment and protection.
• In this case, the embryo grows inside an organ in the abdomen, called the uterus.
• A special organ, called the placenta, feeds the embryo through the umbilical cord.
• Embryonic development ends with birth. This is typical of mammals.

Oviparous Development

• The embryo develops inside an egg, normally outside the female body.
• Most parents incubate the egg to keep it at a specific temperature and to protect it from predators.
• Embryonic development ends when the egg hatches. This is typical of reptiles and fish.

The process of hatching occurs when the new being breaks its egg and emerges:

1. The embryonic development inside the eggs begins inside the female.
2. The egg is laid in a nest.
3. The egg contains the food substances for the embryo.
4. The new being breaks the shell and leaves the egg.

Ovoviviparous Development

• The embryo develops inside an egg which remains inside the female’s body until it hatches.
• Examples include sharks and some snakes.

Does Asexual Reproduction Occur in Plants?

Asexual reproduction is common in plants. It involves the formation of new individuals from the cells of a single parent. There are two main types:

Spore Formation

The nucleus of the parent cell divides repeatedly into a number of daughter cells, called spores. These spores become new individuals without attaching themselves to other cells.

Vegetative Reproduction

Plants create new individuals from a particular organ, usually from the stem. Examples include:

• Bulbs: Underground stems with thick leaves containing nutrients. These nutrients feed the shoot which will become a new plant (e.g., tulips).
• Stem Tubers: Underground stems with a reserve of nutrients and buds. These stems become new plants (e.g., potatoes).
• Stolons: Aerial stems which root when they touch the ground and produce new stems. If stolons are separated from the mother plant, they become new plants (e.g., strawberries).