Download Chapter 22 Plant Diversity

Chapter 20 Plant Diversity
20-1 Introduction to plants
gametophyte: haploid, or gamete-producing phase of an organism
sporophyte: diploid, or spore-producing phase of an organism
What is a plant?
1. multicellular eukaryote
2. cell walls made of cellulose
3. develop from multicellular embryo
4. carry out photosynthesis
5. Ex. trees, shrubs, grasses, moss, ferns
6. most are autotrophs
7. few are heterotrophs and live on decaying materials
General parts of plants:
o Roots – underground organs that absorb water and minerals
o Leaves – photosynthetic organs that contain one or more bundles of
vascular tissue.
o Veins – found inside leaves; made up of xylem and phloem.
o Stems – supporting structures that connect roots and leaves; carry
water and nutrients between them. Ferns have underground stems called
rhizomes.
What do plants need to survive?
1. sunlight – photosynthesis
2. water and minerals
3. gas exchange – O2 for respiration, CO2 for photosynthesis
4. movement of water and nutrients; plants take up water and minerals through root
system, but make food in their leaves
*Land plants evolved from green algae.
Plants have adaptations that allow them to live on land.
1. Challenges of living on land have selected for certain plant adaptations.
2. A cuticle allows plants to retain moisture.
- waxy, waterproof layer
3. Stomata are tiny holes in the cuticle, controlled by guard cells, that allow carbon
dioxide and oxygen to diffuse in and out of the leaf.
4. A vascular system allows resources to move to different parts of the plant.
5. Lignin makes the cell walls rigid which allows plants to grow upright
and tall.
6. Pollen grains allow for reproduction without free-standing water.
7. A seed is a storage device for a plant embryo.
Plants evolve with other organisms in their environment.
Plants and other organisms can share a mutualistic relationship.
–a mutualism is an interaction in which two species benefit
–plant roots and certain fungi and bacteria
–flowering plants and their animal pollinators
20-2 Bryophytes – seedless, non-vascular plants
Bryophytes have life cycle that depend on water for reproduction. They lack vascular
tissue. These plants can draw up water by osmosis only a few centimeters above the
ground.
These include: mosses, liverworts, hornworts
Club mosses and ferns are seedless vascular plants.
A vascular system allows club mosses and ferns to grow higher off the ground.
Vascular tissue is a type of tissue that is specialized to conduct water and nutrients
through the body of the plant.
2 types of vascular tissue:
1. xylem – conducts water(consists of tracheids which move water by capillary
action) If xylem were destroyed, the plant would have no way to conduct water.
2. phloem – conducts nutrients (sugar)
*Ferns produce spores in sporangia, but also have swimming gametes.
**Both need free-standing water for reproduction.
Seed plants include cone-bearing plants and flowering plants.
Seed plants have several advantages over their seedless ancestors.
–can reproduce without free-standing water, via pollination
Gymnosperms – bear seeds directly on the surface of cones (naked seeds)
The cones are the reproductive structures in Gymnosperms.
Ex: conifers (pine, spruce) – most ancient seed plants*
Angiosperms have seeds enclosed in some type of fruit.
Ex: grasses, flowering trees, shrubs, wild flowers
The flowers are the reproductive structures in Angiosperms. Seeds are produced in
the ovaries (most recently evolved structure). The seed includes:
plant embryo, food supply, and protective seed coat.
20-3 Largest Phylum in the plant kingdom is flowering plants
Flowering plants have unique adaptations allowing them to dominate in today’s world.
•Flowers allow for efficient pollination. The stamen is the male reproductive structure
(pollen grains contain the sperm). The pistil or carpal is the female reproductive structure.
–animals feed on pollen or nectar
–pollen is spread from plant to plant in process
•Fruit allows for efficient seed dispersal. Animals eat the fruit and disperse seeds by
passing them out of their body. They can also carry seeds on fur/feathers.
Botanists classify flowering plants into two groups based on seed type.
•A cotyledon is an embryonic “seed leaf.”
•Monocots have a single seed leaf.
–leaf veins usually parallel (ex. Lily)
–flower parts usually in multiples of 3
–bundles of vascular tissue scattered in stem
•Dicots have two seed leaves.
•leaf veins usually branch (ex. Tomato)
•flower parts usually in multiples of 4/5
•bundles of vascular tissue in a ring
Flowering plants are also categorized by stem type and lifespan.
•Stem type can be woody or herbaceous.
–Wood is a fibrous material made up of dead cells.
–Wood has high concentrations of lignin and cellulose.
–Woody stems are stiff.
•There are three types of plant life spans.
- Biennials take two years to compete life cycle. (ex. Celery)
–Annuals mature from seed, flower, and die in one year. (ex. Wheat)
- Perennials – live more than 2 years (ex. Grasses)
20-4 Plants in Human Culture
Agriculture provides stable food supplies for people in permanent settlements.
•Botany is the study of plants.
•Ethnobotany explores how people in different cultures use plants.
•People started planting for harvest about 10,000 years ago.
Plant products are important economic resources.
•Plant products have been traded for thousands of years.
–spices commonly used as currency in Middle Ages
•Plant products contribute to economy on a global scale today.
Plant compounds are essential to modern medicine.
•Pharmacology is the study of drugs and their effects on the body.
•Many drugs are derived from plants.
–Salicin from willow trees is used in aspirin.
–Alkaloids are potent plant chemicals that contain nitrogen.
–Alkaloids such as taxol have anti-cancer properties.