Chapter 22 Introduction to Plants
Terms in this set (56)
Characteristics of Plants
Classified as members of the Kingdom Plantae. Plants are Eukaryotes that have cell walls containing cellulose and carry out photosynthesis using chlorophyll a and b located in chloroplasts. Most plants are autotrophs, a few are parasites or saprobes.
What plants need
Sunlight: Plants use energy from sunlight to carry out photosynthesis so they have adaptations on their leaves to maximize light absorption.
Gas Exchange: plants need oxygen for cellular respiration and they need carbon dioxide for photosynthesis. They release oxygen into the atmosphere and soil.
Water and Minerals: plants need water for photosynthesis. thus, plants have structures that limit water loss and speed the uptake of water from the ground. Plants absorb water and minerals from the soil.
Origins in the water
Ancestors of today's plants were water dwelling organisms similar to today's green algae. most of these were unicellular.
Now considered part of plant kingdom because it has cell walls and photosynthetic pigments identical to those of plants. Also, it has reproductive cycles similar to plants and their genomes suggest that they are closely related to plants.
The first land plants
First land plants lacked leaves and roots which made it hard to obtain water. Fossils suggest first land plants were dependent on water to complete their life cycle. Over time, the demands of life on land favored the evolution of plants more resistant to the drying rays of the sun, more capable of conserving water, and capable of reproducing without water. The appearance of plants on land changed the rest of life on Earth.
Major Groups of Plants
Green Algae, Mosses, Ferns, Cone-bearing plants, and Flowering Plants. These Five major plant groups are based on four important features: embryo formation, specialized water-conducting tissues, seeds, and flowers.
The plant life cycle
The life cycle of land plants has two alternating phases, a diploid (2n) and a haploid (N) phase. This sexual life cycle sets plants apart from other living organisms.
** A sporophyte produces haploid spores through meiosis. These spores grow into multicellular structures called gametophytes. Each gametophyte produces reproductive cells called gametes - sperm and egg cells. During fertilization, a sperm and egg cell fuse producing a diploid zygote. The zygote develops into a new sporophyte and the cycle begins again.
Alternation of generations
The shift between haploid and diploid phases in the plant life cycle.
Sporophyte (spore producing plant)
the multicellular diploid (2N) phase of the plant life cycle
Gametophyte (gamete producing plant)
The multicellular haploid (N) phase. Haploid (N) carries one set of chromosomes, while diploid (2N) have two sets of chromosomes.
Trends in plant Evolution
Over time there has been a reduction in size of the gametophyte and an increase in the size of the sporophyte. This size difference is seen especially in seed plants which have an even smaller gametophyte contained within sporophyte tissues.
Green algae were the first plants on the earth. Evident in the fossil record from the Cambrian period. Green algae are mostly aquatic. They are found in fresh and salt water, and in some moist areas on land. Most are single cells or branching filaments so they make direct contact with the water in which they grow. Therefore, they do not contain the specialized tissues for obtaining water found in other plants. They have cell walls and photosynthetic pigments.
Green Algae Life Cycle
Many have life cycles that switch back and forth between haploid and diploid phases, but they may not alter every generation. EX: The single celled green alga Chlamydomonas. It can switch from asexual reproduction to sexual reproduction as environmental conditions change. If conditions are favorable, the haploid cell reproduces asexually by mitosis. If environmental conditions become unfavorable, Chlamydomamas can switch to a stage that reproduces sexually. P. 640.
Green Algae Mulitcellularity
Many green algae from colonies. Spirogrya forms long, threadlike colonies called filaments. Volvox colonies are more complex than the spirogyra, cells are arranged to form hollow spheres. Volvox cells are connected to one another by strands of cytoplasm, enabling them to communicate.
Group of plants that have specialized reproductive organs enclosed by other, non reproductive cell. Bryophytes are small because they lack vascular tissue. = MOSSES. They have a higher degree of cell specialization than do the green algae.
bryophytes. short, soft plant. thin waxy coating that make it possible for them to resist drying, and thin filaments knows as rhizoids that anchor them to the skid. The RHIZOIDS absorb water and minerals from the soil. Mosses do not have vascular tissue. They do not have strong cell walls so they cannot support a tall plant body = why mosses are small and close to the ground.
specialized tissue in land plants that contains tubes hardened with lignin that enable them to carry water. Bryophytes do not make lignin and do not contain true vascular tissue.
Life cycle of Mosses (Bryophytes)
byrophytes display alternation of generations. Gametophyte is the dominant, recognizable stage of the life cycle. The gametophyte is the stage that caries out most of the plants photosynthesis. The sporophyte is dependent on the gametophyte for its supply of water and nutrients. They depend on water for reproduction because the sperm cell must swim to an egg cell so bryophytes must live in an environment where open water is available at least part of the year.
as the gametophyte grows, it forms rhizoids that from into the ground and shoots that grow into the air. These shoots turn into the familiar green moss plants. Gametes are formed in reprodutive structures at the tips of gametophytes. Some bryophyte species produce both sperm and eggs on the same plant, others produce sperm and eggs on separate plants. Sperm and egg cells fuse to produce a diploid zygote.
where eggs are produced in the gametophyte.
where sperm are produced in the gametophyte.
The zygote produced in the gametophyte phase marks the beginning of the sporophyte stage of the life cycle. It develops into a multicellular embryo growing within the body of the gametophyte. It grows out of the gametophyte and develops a long stalk ending in a capsule.
The spore capsule that grows out of the bryophyte gametophyte. Inside the capsule, haploid spores are produced by meiosis. The capsule ripens and opens, and haploid spores are scattered to the wind to start the cycle again. P. 642
Fossil evidence shows plants developed vascular tissue to carry water and nutrients and were thus able to grow high above the ground. The vascular tissues in these plants - xylem and phloem, make it possible for vascular plants to move fluids through their bodies against the force of gravity.
Also known as vascular plants, after a specialized type of water-conducting cell they contain. Include all seed bearing plants, but vascular tissue is also found in plants that do not produce seeds.
Water conducting cells in vascular plants. They are hollow tubelike cells with thick cell walls strengthened by lignin. One of the great evolutionary innovations of the plant kingdom. They are found in xylem where they are connected end to end like a series of tin cans. Openings between tracheids, called pits, enable water to move more efficiently through a plant than by diffusion alone.
where the tracheids are found. Xylem is a tissue that carries water upward from the roots to every part of a plant.
transports solutions of nutrients and carbohydrates produced by photosynthesis. the main cells of phloem are long and specialized to move fluids throughout the plant body.
Seedless vascular plants.
these vascular plants include club mosses, horesetails, and ferns. Ferns are the most numerous seedless vascular plants. They have true vascular tissues, strong roots, creeping or underground stakes called rhizomes, and large leaves called fronds.
Vascular Plant Life cycle
Ferns and other vascular plants have a life cycle in which the diploid sporophyte is the dominant stage. Haploid spores grow into thin, heart-shaped haploid gametophytes (N). The gametophyte grows independently of the sporophyte. Sperm and eggs are produced on these gametophytes in antheridia and archegonia. Fertilization requires at least a thin film of water so sperm can swim to egg. The Diploid (2N) zygote produced immediately begins to develop into a new sporophyte plant. as the sporophyte matures, haploid (N) spores develop and the cycle begins again.
a plant embryo and a food supply, encased in a protective covering. It contains a living, diploid (2N), plant that represents the early developmental stage of the sporophyte phase of the plant life cycle.
The first seed plants
Ancestors of seed plants evolved new adaptations that allowed seed plants to reproduce without open water. These adaptations include a reproductive process that takes place in cones or flowers, the transfer of sperm by pollination, and the protection of embryos in seeds. In seed plants, the male gametophyte and the female gametophytes grow and mature directly within the sporophyte.
Cones and flowers.
reproductive structures within seed plants where the gametophytes develop. Seed plants are divided into two groups based on which structures they have.
(naked seed) Cone bearing plants. They bear their seeds directly on the scales of the cones. Male cones produce male gametophytes (pollen grains), Female cones produce female gametophytes which are directly on the inside surface of scales (seed cones).
Flowering plants. They bear their seeds in flowers inside a layer of tissue that protects the seed. Most flowers produce both male gametophytes (pollen grains) and female gametophytes in each flower. Some species have separate male and female flowers.
a tiny structure in seed plants containing the entire male gametophyte. Sperm produced by this gametophyte do not swim through water to fertilize eggs, instead they float through the air attaching to people and animals to travel ti the female reproductive structure.
After fertilization, the zygote contained within a seed grows into a tiny plant, the sporophyte embryo.
protective coating that surrounds and protects the embryo and keeps the contents of the seed from drying out. seeds can survive tough conditions. 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.
Lifecycle of a Gymnosperm
reproduction takes place in cones which are produced but the mature sporophyte plant. Pollen cones, male cones, produce pollen grains. One of the haploid (N) nuclei in the pollen grain will divide later to produce two sperm nuclei. Seed cones, or female cones, produce female gametophytes Near the based of each scale of the seed cone are two ovules, the structures in which the female gametophytes develop. Meiosis produces haploid (N) cells that grow and divide to produce female gametophytes.
Gymnosperm Pollination and Fertilization
Conifer lifecycle takes 2 years to complete. Cycle begins in spring as male cones release tons of pollen grains that are carried away by the wind where some reach female cones. There, pollen grains are caught in a sticky secretion on the scales of the female cone and pulled inside toward the ovule. ****In gymnosperms, the direct transfer of pollen to the female cone allows fertilization to take place without the need for open water. most use wind pollination.
structure in a plant that contains two haploid sperm nuclei. Once the pollen tube reaches the newly formed female gametophyte within the ovule, one sperm nucleus disintegrates, the other fertilizes the egg contained within the female gametophyte. A diploid zygote is produced which grows into an embryo, the new sporophyte plant. the embryo is then encased to form a seed.
Flowers and Fruit
Angiosperms. most abundant organisms in plant kingdom. their origin in the Cretaceous period makes them the most recent of all plant phyla. Angiosperms develop reproductive organs called flowers. Flowers contain ovaries which surround and protect the seeds. Angiosperms reproduce sexually by means of flowers. After fertilization, ovaries within flowers develop into fruits that surround, protect, and help disperse seeds.
advantages of flowers
flowers are an evolutionary advantage because they attract animals such as bees, moths or hummingbirds who carry pollen with them as they leave. because these animals travel from flower to flower, pollination is much more efficient than the wind pollination of most gymnosperms.
advantages of fruits
after pollination, the ovary develops into a fruit. the fruit is a structure containing one or more matured ovaries. The wall of the fruit helps disperse the seeds inside it, carrying them away from the parent plant. seeds from the fruit enter an animals digestive system and are left far away from the original plant, thus spreading seeds over hundreds of kilometers.
seed leaves in an angiosperm embryo. This was first used to classify flowering plants.
angiosperm embryos with one seed leaf or cotyledon.
angiosperm embryo with two seed leaves or cotyledons.
"ancient fruit" It is the oldest known plant with reproductive organs like those found in modern flowers. It is more ancient than modern day monocots and dicots and cannot be classified as either.
scientific classification now places monocots into a single group but places the dicots in a variety of distinct and different categories, so the term dicot is no longer used for classification.
1. Amborella Clade: oldest branch of angiosperms. Its floral parts have a spiral arrangement.
2. Water Lily Clade: another very old group.
3. Magnoliids: contains a wide range of floral diversity, from species with small plain flowers to the dinner-plate sized Magnolia flower.
4. Monocots: contains about 20% of all angiosperms. Includes several important crop species such as rice, corn and wheat as well as orchids, lilies and irises.
5. Eudicots: 75% of angiosperms are eudicots. this clade is nearly as old as angiosperms themselves. They diversified tremendously several times in history.
angiosperms are often grouped according to the number of their seed leaves, the strength and composition of their stems, and the number of growing seasons they live. These categories can overlap.
Monocots and Dicots
angiosperms may be termed monocots or dicots based on the number of seed leaves, or cotyledons, they produce. Monocots and dicots differ in characteristics such as the distribution of vascular tissue in stems, roots and leaves, and the number of petals per flower.
Monocots = corn, wheat, lilies, orchids and palms. Monocot grasses, wheat, corn and rice, are the first plants to be cultivated for food.
Dicots = roses, clover, tomatoes, oaks, daisies.
seeds = single cotyledon
leaves = parallel veins
flowers = floral parts often in multiples of three
stems = vascular bundles scattered throughout stem
roots = fibrous roots
seeds = two cotyledons
leaves = branched veins
flowers = floral parts often in multiples of 4 and 5
stems = vascular bundles arranged in a ring
roots = taproot
woody and herbaceous plants
plants can be subdivided into groups based on the characteristics of their stems.
1. woody plants: are made primarily of cells with thick cell walls that support the plant body. Include trees, shrubs, and vines.
2. herbaceous plants: stems are smooth and nonwoody. they do not produce wood as they grow. EX: dandelions, zinnias, petunias and sunflowers.
comparing plants by Life Span
1. annuals: grow from seed to maturity, flower, produce seeds, and die in just one growing season. EX: tomatoes, wheat.
2. Biennials: year 1: sprout and grow very short stems and sometimes leaves. Year 2: grow new stems and leaves, flower, produce seeds, then die. EX: parsley, celery, evening primroses
3. Perennials: most have woody stems. Some have herbaceous stems that die each winter and are replaced in the spring. EX: many grasses, palm trees, maple trees.
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