Ch.8 Plants

Section 4: Gymnosperms and Angiosperms A gymnosperm is a seed plant that produces naked seeds (not being enclosed by a protective fruit) Every gymnosperm produces naked seeds. In addition, many gymnosperms have needle-like or scale-like leaves, and deep-growing root systems Oldest type of seed plant Four types: cycads, conifers, ginkgoes, and gnetophytes

Section 4: Gymnosperms and Angiosperms Cycads Grow mainly in tropical and subtropical areas; look like palm trees w/ cones, & grow as big as a football Conifers Cone-bearing, & largest/most diverse groups Ex: pines, sequoias, junipers, are evergreens Keep there leaves year round Ginkgoes Only one species living today & are planted along city streets because they can tolerate air pollution Gnetophytes Live in hot desert & tropical rain forest

Section 4: Gymnosperms and Angiosperms Reproduction in Gymnosperms Most gymnosperms have reproductive structures called cones (are covered with scales) Form two types of cones: male and female Single plants produce both male/female but some trees produce either male/female but some produce no cones at all The female gametophyte develops in structures called ovules (is a structure that contains an egg cell) First, pollen falls from a male cone onto a female cone. In time, a sperm cells and an egg cell join together in an ovule on the female cone After fertilization occurs, the seed develops on the scale of the female cone

Section 4: Gymnosperms and Angiosperms Reproduction in Gymnosperms Pollination The transfer of pollen from a male reproductive structure to a female reproductive structure is called pollination; wind carries the pollen from male to female; the pollen collects is a sticky substance produced by each ovule Fertilization The ovule closes and seals in the pollen; the scale close, and a sperm cell fertilizes an egg cell inside each ovule; then develops into the embryo part of the seed

Section 4: Gymnosperms and Angiosperms Reproduction in Gymnosperms Seed Development Female cones remain on the tree while the seeds mature; the seed develops increasing in size which could take up to two years Males cones fall off the tree after they have shed their pollen Seed Dispersal When the seeds are mature, the scales open; the wind shakes the seeds out of the cone and carries them away

Section 4: Gymnosperms and Angiosperms All angiosperms, or flowering plants, share two important traits. First, they produce flowers. Second, in contrast to gymnosperms, which produce uncovered seeds, angiosperms produce seeds that are enclosed in fruits

Section 4: Gymnosperms and Angiosperms The Structure of Flowers Flowers come in all sorts of shapes, sizes, and colors. But, despite their differences, all flowers have the same function – reproduction A flower is the reproductive structure of an angiosperm Sepals and Petals When a flower is still a bud, it is enclosed by leaflike structures called sepals (protect the developing flower and are often green in color) When the sepals fold back, they reveal the flower’s colorful, leaflike petals (most colorful part of the flower)

Section 4: Gymnosperms and Angiosperms The Structure of Flowers Stamens The stamens are the male reproductive parts The thin stalk of the stamen is called the filament Pollen is produced in the anther, at the top of the filament Pistils The female parts, or pistils are found in the center of most flowers (some flowers have 2 or more) The sticky tip of the pistil is called the stigma A slender tube, called a style, connects the stigma to a hollow structure at the base of the flower This hollow structure is the ovary, which protects the seeds as they develop

Section 4: Gymnosperms and Angiosperms The Structure of Flowers Pollinators To ensure that pollination occurs the colors and shapes of most petals and the scents produced by most flowers attract insects and other animals Reproduction in Angiosperms First, pollen falls on a flower’s stigma. In time, the sperm cell and egg cell join together in the flower’s ovule. The zygote develops into the embryo part of the seed

Section 4: Gymnosperms and Angiosperms Reproduction in Angiosperms Pollination Pollinated when a grain of pollen falls on the stigma, by the wind, birds, bats, or insects Nectar, a sugar-rich food, is located deep inside a flower; when an animal enters a flower to get the nectar, it brushes against the anthers and becomes coated with pollen dropping the pollen onto the stigma Fertilization Fertilization occurs when pollen falls on the stigma A sperm cell joins with the egg cell inside the ovule, then the zygote begins to develop into the seed’s embryo

Section 4: Gymnosperms and Angiosperms Reproduction in Angiosperms Fruit Development and Seed Dispersal As the seed develops after fertilization, the ovary changes into a fruit – a ripened ovary and other structures that enclose one or more seeds Fruits are the means by which angiosperm seeds are dispersed Types of Angiosperms Angiosperms are divided into two major groups: monocots (are angiosperms that have only one seed leaf) and dicots (produce seeds with two seed leaves)

Section 4: Gymnosperms and Angiosperms Types of Angiosperms Monocots Ex: corn, wheat, rice, lilies, and tulips Have 3 petals or a multiple of three petals Have long, slender leaves with veins that run parallel to one another Stems are scattered randomly throughout the stem Dicots Ex: roses, violets, dandelions, oak/maple trees, beans, and apples Four or five petals Leaves are wide, with veins that branch many times Stems have bundles of vascular tissue arranged in a ring

Section 4: Gymnosperms and Angiosperms Seed Plants in Everyday Life Provide useful products such as paper and the lumber used to build homes Conifers are used to produce turpentine, & rayon Angiosperms are important source of food, clothing, and medicine People eat vegetables, fruits, and cereals, which all are angiosperms