Chapter 24 Notes - Introduction to Plants
1.Adaptations of Plants
A.Plants are the dominant group of organisms on land by weight; they are very diverse in size, shape, structure, and function
B.Plants may have evolved from photosynthetic green algae found in the water, plants had to adapt to life on land by developing specialized structures
1.Roots - used to obtain water and nutrients, the first roots may have developed from a symbiotic relationship (called mycorrhizae) between the underground parts of plants and fungi, this relationship still exists in 80% of modern plants
2.Cuticle - water-tight and waxy covering that prevents water loss, covers all non-woody parts of the plants; the stomata are pores in the cuticle that allow for the exchange of gasses; two guard cells border each stoma and change shape to allow the stoma to open and close
3.Pollen - structures that enclose sperm, allow sperm to be transported without water and prevents them from drying out
C.Transport of water and nutrients
1.Vascular plants - use a vascular system of specialized cells arranged in strands that act like a pipeline for nutrients and water
2.Non-vascular plants - relatively small plants that lack vascular tissue and absorb nutrients and water by osmosis and diffusion
D.Reproduction by seeds (found in angiosperms and gymnosperms)offers several advantages
1.Protection - seeds are surrounded by a seed coat that prevents drying, injury, and disease
2.Nourishment - seeds contain nutrients to feed the embryo as it begins to grow
3.Plant dispersal - many seeds have structures that allow them to be spread by wind, water, or animals; dispersal limits competition between parents and offspring
4.Delayed growth - seeds hold the embryo in a state of suspended animation until conditions are favorable for growth
E.Flowers offer other advantages
1.Produce both pollen and seeds making reproduction more efficient by reducing the need to use wind as the means of cross-pollination
2.Attract animals that carry smaller amounts of pollen longer distances than wind
2.Alternation of Generations (pgs 152 & 524)
A.Plants reproduce in two phases that alternate
1.Sporophyte - diploid individual (formed from zygote after fertilization) that produces spores by meiosis
2.Gametophyte - haploid individual (formed from spores) that produces gametes by mitosis
B.Non-vascular plants have a dominant (more noticeable) gametophyte generation
C.Vascularplants have a dominant (more noticeable) sporophyte generation, marked by several special features
1.Xylem & Phloem - carry water, minerals, and organic nutrients throughout the plant allowing for growth to great heights
2.Shoot - upward growing body of the plant
3.Root - downward growing body of the plant
4.Meristems - actively dividing plant cells that promote growth
5.Leaves & stems - grow from the shoot
3.Kinds of Plants
A.Non-vascular plants
1.Key Features
a)Lack a vascular system
b)Small in size and relatively simple in structure, water and nutrients transported by osmosis and diffusion
c)Larger gametophyte than sporophyte, have hair-like projections called rhizoids that anchor the gametophytes to the surface on which they grow, sporophytes grow on the gametophyte and depend on them for nutrition
d)Require water for sexual reproduction, egg and sperm grow in separate structures, often on separate plants, the gametophytes grow in tightly packed mats and sperm swim through a coating of water to reach the eggs
2.Types
a)Mosses (phylum Bryophyta)
b)Liverworts (phylum Hepatophyta)
c)Hornworts (phylum Anthocerophyta)
B.Seedless Vascular Plants
1.Key Features
a)Do not produce seeds
b)Have a vascular system with xylem and phloem reinforced with lignin which is a major component in wood; this system allows vascular plants to grow larger and become more complex than non-vascular plants
c)Sporophytes are larger than gametophytes making it easier for the wind to carry spores increasing dispersal efficiency
d)Smaller gametophyte develop under the soil and require water for fertilization
e)Spores are drought resistant and make it possible for a plant to live in drier habitats
2.Types
a)Ferns (phylum Pterophyta)
b)Club Mosses (phylum Lycophyta)
c)Horsetails (phylum Sphenophyta)
d)Whisk ferns (phylum Psilotophyta)
4.Two types of Seed (Vascular) Plants (Gymnosperms & Angiosperms)
A.Gymnosperms - seed plants without flowers or fruits to contain seeds
1.Key Features
a)Seeds that protect the embryo and provide it with nutrients, allow it to survive adverse conditions, and allow for plant dispersal away from parents
b)Cones - tiny gametophytes are male or female and form within the sporophyte in male and female cones
c)Wind pollination - sperm do not need water to travel allowing for pollination in dry conditions
2.Types
a)Conifers (phylum Coniferophyta)
b)Cycads (phylum Cycadophyta)
c)Ginko (phylum Ginkophyta)
d)Gnetophytes (phylum Gnetophyta)
B.Angiosperms - seed plants with flowers and fruits to contain seeds; the majority of plants are part of this group
1.Key Features
a)Flowers - male and female gametophytes develop within flowers which are more efficient than cones for pollination
b)Fruits - structures in which the seeds develop, their primary function is seed dispersal
c)Endosperm - stores of food for the developing embryo as the seed begins to mature
2.Kinds (two groups)
a)Monocots - produce seeds with one seed leaf (cotyledon), produce flowers with parts in multiples of three and long narrow leaves with parallel veins
b)Dicots - produce seeds with two seed leaves (cotyledons), also produce flowers with parts in multiples of two, four or five parts with leaves with branching, netted veins
5.Plants Provide Food
A.Fruits and Vegetables
1.Classified nutritionally one way, in botany fruits are the reproductive part of the plant which contains seeds, and vegetables are any non-reproductive part of the plant
2.Both provide dietary fiber and essential vitamins and minerals
B.Root Crops
1.Any plant root eaten as food, including carrots, radishes, turnips and beets, these vegetables are enlarged roots that store starch
2.Potatoes and Yams (sweet potatoes) are also classified as root crops but are actually tubers (modified underground stems that store starch)
C.Legumes
1.Members of the pea family
2. Include soybeans, peas, peanuts, and many types of beans
D.Cereals
1.Grasses that produce a large number of dry edible fruit called grains
2.Includes wheat, corn, rice, oats, & sugar cane
6.Plants as Products
A.Wood/Paper
1.After food, single most valuable resource obtained from plants
2.Used in building, producing products like paper and rayon
B.Medicine
1.Throughout history plants have been used to treat ailments
2.Today many of our common and prescription medicines are derived from plants
C.Fibers
1.Strands of cellulose from the plant cell body
2.Used in making cloth, paper, and rope
D.Rubber
1.Made from the sap of the rubber tree called latex
2.Used in many products including boots, raincoats, and storage devices