Evolution of Plants

Matter is recycled in the environment within and between ecosystems. All organisms require nitrogen to make amino acids, which are used to build proteins and nucleic acids, which combine to form DNA and RNA. The Nitrogen Cycle

Although nitrogen gas is the most abundant form of nitrogen on Earth, only certain types of bacteria that live in the soil and on the roots of legumes can use this form directly. The bacteria convert nitrogen gas into ammonia, in a process known as nitrogen fixation. The Nitrogen Cycle

Other soil bacteria convert fixed nitrogen into nitrates and nitrites that plants can use to make proteins and nucleic acids. Heterotrophs eat the plants and reuse nitrogen to make their own nitrogen-containing compounds. The Nitrogen Cycle

The greatest challenge that early land plants faced was obtaining water. They met this challenge by growing close to the ground in damp locations. Fossils suggest the first true plants were still dependent on water to complete their life cycles. One of the earliest fossil vascular plants was Cooksonia, shown here. The First Land Plants

Several groups of plants evolved from the first land plants. One group developed into mosses. Another lineage gave rise to ferns, cone-bearing plants, and flowering plants. The First Land Plants

Botanists divide the plant kingdom into five major groups based on four important features: embryo formation, specialized water-conducting tissues, seeds, and flowers. An Overview of the Plant Kingdom

Vascular tissue—xylem and phloem—make it possible for vascular plants to move fluids through their bodies against the force of gravity. Vascular Plants

Vascular plants are known as tracheophytes, after a specialized type of water- conducting cell they contain. These cells, called tracheids, are hollow tubelike cells with thick cell walls strengthened by lignin. Vascular Plants

Tracheids are found in xylem, a tissue that carries water upward from the roots to every part of a plant.Xylem

Vascular plants also have a second transport tissue called phloem that transports solutions of nutrients and carbohydrates produced by photosynthesis.Phloem

Among the seedless vascular plants alive today are three phyla commonly known as club mosses, horsetails, and ferns. The most numerous of these are the ferns. Ferns can thrive in areas with little light and are most abundant in wet habitats. Seedless Vascular Plants

Every seed contains a living plant ready to sprout as soon as it encounters the proper conditions for growth. The production of seeds has been one key to the ability of plants to colonize even the driest environments on land. The Importance of Seeds

A seed is a plant embryo and a food supply, encased in a protective covering. Seed Plants

In seed plants, the male gametophytes (sex cells) and the female gametophytes grow and mature directly within the sporophyte(adult plant cells). The gametophytes usually develop in reproductive structures known as cones or flowers. Cones and Flowers

Nearly all gymnosperms bear their seeds directly on the scales of cones. Cones and Flowers

Flowering plants, or angiosperms, bear their seeds in flowers inside a layer of tissue that protects the seed. Cones and Flowers

In seed plants, the entire male gametophyte is contained in a tiny structure called a pollen grain. Pollen grains are carried to the female reproductive structure by wind or animals such as insects. The transfer of pollen from the male reproductive structure to the female reproductive structure is called pollination.Pollen

Pollen in gymnosperms must be carried by the wind.Pollen

Pollen in angiosperms is mostly carried by insects and larger animals.Pollen

After fertilization, the zygote contained within a seed grows into a tiny plant—the sporophyte embryo. A tough seed coat surrounds and protects the embryo and keeps the contents of the seed from drying out.Seeds

The embryo begins to grow when conditions are right. It does this by using nutrients from the stored food supply until it can carry out photosynthesis on its own.Seeds

A)pollen grain B)spore C) seed D) gametophyte Which of the following includes a plant embryo, a food supply, and a protective covering?

A)swim to female reproductive structures through water. B)must be carried from a male cone or flower to a female cone or flower. C) carry zygotes to the female structures, which form the seeds. D) are carried to female reproductive structures by wind or animals. During pollination in seed plants, pollen grains

A)flowers. B)cones. C) embryos. D) ovules. The gametophytes of gymnosperms are found inside reproductive structures called

Angiosperms – flowering plantsAngiosperms

Angiosperms develop unique reproductive organs known as flowers, shown in the figure. Flowers contain ovaries, which surround and protect seeds. Flowers and Fruits

Flowers are an evolutionary advantage to plants because they attract animals that carry pollen with them to the next flower they visit. This means of pollination is much more efficient than the wind pollination of most gymnosperms. Advantages of Flowers

After pollination, the ovary develops into a fruit, a structure containing one or more matured ovaries.Fruit

When an animal eats a fleshy fruit, seeds from the fruit enter the animal’s digestive system. By the time the seeds leave the digestive system, the animal may have traveled many kilometers. By using fruit, flowering plants increase the ranges they inhabit.Fruit

Seed leaves in their embryo o Monocot – 1 seed leaf o Dicot – 2 seed leavesCotyledons

Scientific classification places the monocots into a single group but places the dicots in different categories. Angiosperm Classification

The characteristics of monocots and dicots are compared in the table below. Monocots and Dicots

Woody plants are made primarily of cells with thick cell walls that support the plant body. Herbaceous plants have stems that are smooth and nonwoody. Woody and Herbaceous Plants

Annuals, Biennials and Perennials

A)pollen grains. B)cones. C) ovaries. D) petals. Angiosperms produce seeds inside protective structures called

A)annuals. B) dicots. C) perennials. D) biennials. Flowering plants that grow, flower, produce seeds, and die in one year are called