Seed Plants

Gymnosperms & Angiosperms

Seeds

• Seeds are a major adaptation of land plants that allow for reproduction without water

• As such, plants like gymnosperms and angiosperms can be found in almost any climate

Seeds

• A seed is an embryo (sperm & egg have fused)

– It contains a protective covering – seed coat– It also has a food supply

Seeds

• Gymnosperms produce seeds inside of cones• Angiosperms produce seeds inside of flowers

Pollen

• A pollen grain is often thought of as the equivalent to a sperm cell, but it is actually the entire male gametopyhte

• The sperm produced inside a pollen grain do not swim, they are carried to the egg by wind, insects or animals– This is known as pollination

Cones

• Cones are the structures that gymnosperms use to produce both male and female gametophytes

• Male cones produce pollen– Contains the “sperm” cells

• Female cones produce ovules – Contains the egg cells

Pollination

• Pollen grains (gametophyte) are carried from the male cone of one plant, to ovules (gametopyhte) in the female cone of another plant.– Can be same plant, but not typically

• Once a gamete from the pollen grain meets the egg inside the ovule, the two cells fuse, eventually making an embryo inside of a seed.

Alternation of generations

• As with ferns, the sporophyte is the dominant stage of the life cycle for gymnosperms.

• Trees like spruce, are the sporophyte, the pollen grains and ovules formed inside of its cones are the gametophyte

Gymnosperms

• Gymnosperms produce seeds that are exposed or naked– They have nothing covering them

– …unlike angiosperms that have a fruit surrounding their seeds.

Angiosperms

• Unlike gymnosperms, their gametes, and eventual seeds are made within flowers

• Whereas gymnosperms produce “naked” seeds, angiosperms have their seeds surrounded by a fruit

Flower Anatomy

Flower Anatomy

Stamen

• The stamen is the male structure of the flowering plant– Anther (makes pollen grains)– Filament (holds anther)

• The pollen grain is the male gametophyte b/c is makes the male gamete

Stamen

Flower Anatomy

Pistil/Carpel

• The pistil is the female structure of a flowering plant

• The pistil may be made up of one or more carpels

• The carpel consists of:– 1 stigma– 1 style – 1 ovary

Pistil/Carpel

Pollination

• Pollination is the act of a pollen grain being transport from the anther (male) to the stigma (female) to allow for fertilization– When this happens within the same flower it is

know as self-pollination

• Insects, birds, and wind are the most common pollinators.

Fertilization

• Once the pollen grain lands on a stigma, the male gametes inside still need to make it to the female gametes in the ovules.

• A pollen tube burrows out from the grain, and down through the style to the ovary and ovules, delivering the sperm cell to the egg cell for fertilization.– Fertilization will result in an embryo within a seed!

Pollen tubes/Fertilization

Petals

• Petals are modified leave of the plants

• They protect the male and female reproductive organs early on

• Usually brightly colored to attract pollinators when the plant is mature

Fruits

• In biology, a fruit is anything that surrounds a seed of a flowering plant

• The ovary, on fertilized becomes the fruit, just as the fertilized ovules become the seeds.

Fruits?

Fruits?

Fruits

• The role of a fruit is to encourage animals to eat them, so that seeds may be carried away from where they were made

• They also serve as a form of added protection in some cases.