Plant Diversity 22-4 & 22-5

Seed PlantsThe seed was major step in the evolution of land plants. It allowed plants to be able to colonize dryer areas of land.

Seed PlantsAdaptations that allow seed plants to

reproduce without water include flowers or cones, the transfer of sperm by pollination, and the protection of embryos in seeds.

Flowers & ConesC ones are the structures on plants such as

pine cones that contain the seedsFlowers are the seed bearing structures on

plants like oak trees and rose bushes.

PollenPollen is the structure that contains the

sperm of the plant. Pollen can be transferred from one flower to another in several ways. What are some ways that pollen can be transferred?

SeedsSeeds are

multicellular structures that contain the developing embryo of a plant. The seeds also contains a stored food supply for the embryo. A seed coat surrounds and protects the embryo as it grows.

Find video of seed growth

Evolution of Seed PlantsAs landmasses on Earth became dryer seed

plants invaded these areas and eventually become the dominant land plant.

GymnospermsAll members of this group have “naked”

seeds – seeds are not enclosed/protected by fruit.

Gnetophytes – reproductive scales are clustered into cones

GymnospermsCycads – palmlike plants that reproduce

with large cones

GymnospermsGinkgoes – phylum contains only one

extant specie(Ginkgo biloba)

GymnospermsConifers are the most

recognizable and most common gymnosperm

Evolution of ConifersThe specialized leaves (needles) of conifers

are adapted to dry, cool environments. The shape of the needle reduces water loss.They have a thick waxy cuticle on the

surface of the needles that also reduces water loss.

Needles contain a lot of resin which reduces the number of herbivores that will eat them because they taste so bad.

Holes for gas exchange are sunken, this reduces water loss.

Angiosperms - Flowering PlantsThe majority of the members of this

phylum have seeds that are enclosed in fruits. Different flower parts give rise the different parts of the fruit.

Angiosperms - Flowering PlantsFlowers contain the reproductive organs of

angiosperms. What evolutionary advantage does a flower give an angiosperm?

Angiosperms - Flowering PlantsFertilization is when the sperm and egg

unite. During seed development the ovary develops into the fruit.

Angiosperms - Flowering PlantsThe fruit of angiosperms is a wall of tissue

surrounding the seed. Fruits are another evolutionary advantage for the success of this group.

Diversity of AngiospermsMonocots vs. Dicots –

named for the number of seed leaves/cotyledons in the plant embryo. Monoctos have one, Dicots have two

Fig. 22-25

Diversity of AngiospermsMonocots vs. Dicots – (con’t)

Diversity of AngiospermsMonocots vs. Dicots – (con’t)