Bio 121 Chapter 28

Alteration of Generations

Gametophyte and Sporophyte

-the sporophyte originated from a fertilized egg and grew directly from the gametophyte’s body

-gametophyte is self-sufficient but sporophyte is dependent on the gametophyte for water and nutrients

The Life Cycle of a Seed Plant

1. Spore formation

2. Gametophyte development

3. Pollination and fertilization

4. Seed maturation

pollen=

male gametophytes

ovule=

female gametophyte

Pollen and Ovule Cones

-pollen cones are typically found in clusters near the bottom branches of the tree and produce spores that will develop into the male gametophyte

-ovulate cones are in the upper branches and produces spores that will develop into the female gametophytes

Seed Cones

-after fertilization takes place in pines, the ovules develop the seeds

-ovulate cones enlarges, becomes woody, and is then referred to as a seed cone

-once the seeds are released, they can grow and mature into new sporophytes

Pollen is formed in…

the sporangia within the anther

Angiosperm Pollination

the pollen reaches the ovules by landing on the stigma, and through cell division of the pollen, a pollen tube grows and extends through the style

Angiosperms, the ovary wall develops into a fruit

1. They serve to protect immature seeds from being preyed upon by animals

2. They enhance dispersal once the seeds are mature

Fruit Development

-essential for fruit not to be consumed before the seeds are able to withstand digestive tract dispersal

-immature fruit flesh and physically tough and tissues are highly astringent

-ripen color, texture, and palatability are rapidly trans.

Fruit & Seed Dispersal

-animals are the most important agents of seed dispersal

-ripe fruits attract animal dispersers who eat the fruit and then at a later time deposit its seeds away from the parent plant

Vegetative Reproduction

-horizonal stems allow new upright grass shoots in lawns to be produced at a distance from the site where the plant parent originally germinated

-vegetative reproduction also occurs in woody plants

-less/no genetic diversity/variation

-lack of movement/location