Savvas Realize Topic 3 Lesson 2

Plant Life Cycles

Plants have two different stages of their life cycle: the sporophyte stage and the gametophyte stage.

• During the sporophyte stage, a plant produces spores that develop into gametophytes.

• In the gametophyte stage, male and female sex cells are produced, which are needed for fertilization.

Nonvascular Plants

• Nonvascular plants (plants that absorb nutrients and water through their surface; moss) produce sporophytes that resemble small trees or flowers. They release spores that grow into gametophytes. Gametophytes produce sperm and egg cells needed to produce a zygote (fertilized egg)

Seedless Vascular Plants

• In seedless vascular plants (ferns), sporophytes produce spores that develop into gametophytes. However, fern gametophytes have both male and female structures that produce sex cells. When fertilization occurs, a new sporophyte begins to develop.

Other Vascular Plants

• Other vascular plants are gymnosperms (cones) and angiosperms (flowers). The male gametophyte in both plants is called pollen, which contain cells that develop into sperm cells. For reproduction to occur, pollen must travel to the female gametophyte so it can fertilize the egg.

Structures for Reproduction

• Plants have evolved body structures that help them reproduce.

Asexual Reproduction in Plants

While most plants reproduce sexualy, many plants reproduce asexually. New plants can grow from the leaves, stems, or roots of a parent plant (ex: potato eyes)

Gymnosperms

• Gymnosperms have needle-like leaves, deep roots, cones, and unprotected seeds. Male cones hold pollen, and female cones hold an ovule (the structure holding an egg).

• The pollen can be transported by the wind and stick to the female cone due to a sticky liquid.

• When this happens, the egg may become fertilized, and a zygote develops into a plant embryo in the seed.

• Once matured, the female cone opens up, and the wind blows the unprotected seeds out.

Angiosperms

Angiosperms have either flowers or fruits that contain seeds.

• The male reproductive structure is called the stamen, including the anthers (which forms the pollen) and filament. The pistil, the female reproductive structure, has 3 parts: the sticky stigma, the style, and the ovary.

Angiosperms (cont.)

• Some angiosperms are pollinated by the wind, but most rely on pollinators, or animals that spread pollen. When pollen falls on the stigma, fertilization may occur. The zygote then develops into the seed's embryo.

• Colorful, often pleasantly-scented petals surround the plant's reproductive organs and attract pollinators. The sepals protect the growing flower. The flower can also develop the fruit - the ripened ovary and its seeds.

Seed Dispersal and Germination

• Fruits are the means by which angiosperm seeds are dispersed. Animals are attracted to the fruit by its scent and color. When it eats the fruit, it spreads the seeds through its droppings. Seeds also disperse through wind and water. Seeds further from the parent plant have a better chance of survival as they don’t have to compete for resources.

• Germination occurs when the embryo sprouts out of a seed.