Download UNIT 4: PLANTAE: Chapters 9, 10, 11

BIOLOGY 11: UNIT 4: Kingdom Plantae: Green Algae, Mosses, Ferns,
Gymnosperms,Angiosperms
Chapters 9, 10, 11
UNIT 4 OBJECTIVES:
GREEN ALGAE, MOSSES, FERNS:
1. Examine green algae, mosses, and ferns and describe characteristics
that unify each.
2. Demonstrate the correct use of the dissection microscope.
3. Explain the benefits of alternation of generations.
4. Use examples of unicellular, colonial, and multicellular green algae to
illustrate their diversity.
5. Describe the ecological roles of green algae, mosses, and ferns.
6. Describe the role of mosses as pioneer plants.
7. Compare and contrast how ferns and mosses have adapted to a land
environment.
GYMNOSPERMS:
1. Describe the characteristics that unify gymnosperms.
2. Explain how gymnosperms are adapted for survival in a land
environment with respect to the following: alternation of generations,
needles, seeds, pollen, and vascular tissue.
3. Explain the role of meristems in primary and secondary stem growth.
4. Evaluate the economic and ecological importance of gymnosperms.
ANGIOSPERMS:
1. Examine angiosperms and describe characteristics that unify them.
2. Compare and contrast the ways in which angiosperms and
gymnosperms have adapted to a land environment.
3. Use specimens to differentiate between moncots and dicots
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UNIT 4: PLANTAE: Chapters 9, 10, 11
Introduction and plant diversity:
Plants have been classified in many ways because there are 300,000 to 500,000 species.
These classifications are based on evolutionary relationships & adaptations.
This textbook classifies plants into 3 groups:
1) Aquatic plants
2) Non vascular plants
3) Vascular plants
Characteristics of all Plants:, p. 245
1.
2.
3.
4.
Eukaryotic.
Cell walls with cellulose.
Alternation of generations in life cycles.
Produce carbohydrates by photosynthesis
5. Lack mobility.
Evolutionary Adaptations by Plants:,
As the environment changed, over time plants adapted structures & systems for:
1) Transport of H2O - root, stems & leaves
2) Method of reproduction that did not depend on H2O for dispersal of gametes.
Life Cycles of Plants Involve 2 Stages:
1) Gametophyte Stage - stage of life cycle that produces haploid gametes (N).
2) Sporophyte Stage - stage of life cycle that produces diploid spores (2n). This stage
arises from the union of 2 haploid gametophytes. In simple plants like mosses, the
sporophyte depends on the gametophyte for water & nutrients. This role is
reversed in complex plants like ferns & seed plants.
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AQUATIC PLANTS: ALGAE:
Characteristics of aquatic plants:, p. 246
1. Mostly multicellular, some are unicellular, filamentous or colonial
2. Simple plants
3. No conductive tissue - no true roots, stems or leaves
4. Live surrounded by water
Water:
1)
2)
3)
4)
Prevents cells from drying out.
Structural support to the plant.
Provides nutrients.
Accommodates the dispersal of spores & meeting of sex cells
Aquatic Plants Belong to One of 3 Divisions:
1. Green Algae: Chlorophyta: (Volvox & Spirogyra)
These are single-celled or multicellular algae containing pigments chlorophyll a, b &
carotene & store starch. Cell walls contain cellulose.
Habitat: fresh water, moist soils, & coastal tropical seas.
Sexual reproduction: involves alternation of generations. Asexual reproduction: by
fragmentation or by spores
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2. Brown Algae: Phaeophyta: (Fucus=Rockweed)
Multicellular algae contain pigments chlorophyll a, c & fucoxanthin & store laminarin &
oils. Cell walls contain cellulose.
Habitat: colder seawater.
Sexual reproduction: involves alternation of generations. Asexual reproduction: by
fragmentation or by spores.
3. Red Algae: Rhodophyta: (Dulse, Irish Moss, Plumaria)
Multicellular algae contain pigments chlorophyll a, d and Carotenes & Phycobilins. Cell
walls contain cellulose & store starch.
Habitat: mainly warmer seawater & some fresh water.
Sexual reproduction: involves alternation of generations. Asexual reproduction: by
vegetative reproduction.
Ecological Role of Aquatic Plants:
Algae play an important role in the global environment. Phytoplankton are primary food
producers and are a source of biological energy for nearly all food webs in aquatic
habitats, they supply about 67% of the global supply of oxygen. Human wastes and
pollutants reduce algae populations. Algae is used to make agar a gel used in labs to
grow bacteria on petri plates. Carrageen is used to make ice cream & pie fillers.
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Reproduction in Algae:, p. 248
Higher algae have complex life cycles incorporating features found in higher plants and
animals.
Sexual Reproduction: This involves the fusion of 2 haploid cells gametes producing
a zygote.
1. Conjugation: union of isogametes, that are identical gametes of different strains (-) &
(+), such as in the Spirogyra.
2. Fertilization: union of heterogametes, that are different gametes (larger = egg) &
(smaller = sperm), such as in the Fucus.
Zygote formation: occurs after sexual reproduction. The zygote may germinate or form
a zygospore: a thick-walled resistant spore, it can survive unfavourable environmental
conditions and then germinates, undergoes meiosis, & grows into mature cells.
Asexual or Vegetative Reproduction:
There is neither cell fusion nor a change in chromosome number. There are 3 methods
of asexual reproduction.
1. Fragmentation: thallus or body part breaks off
2. Formation of spores: motile zoospores & non-motile spores
3. Mitotic Division: in single-celled plants.
<Homework - Review Questions, p. 251 (8 - 15)>
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Importance of Terrestrial Plants:, P. 256
Colonization of land by terrestrial plants occurred more than 400 million years ago and
is one of the major events in the evolution of life.
The transition from aquatic life to life on land took millions of years. Plants transformed
land & created environmental changes. Increasing adaptation of herbivores & their
predators followed.
Problems for Plants that Lived on Land:
1)
2)
3)
4)
5)
6)
7)
Air provides little support to plants.
Obtaining water & nutrients.
Transporting & water, minerals & products of photosynthesis.
Preventing excessive water loss by evaporation.
Gas exchange between plants & air.
Reproduction & protection of the embryo.
Withstanding extreme fluctuations in environmental conditions.
Adaptations of land plants: involve the roots, stems, leaves, and reproduction:
1. Roots: anchor plants in ground & absorb water & nutrients from the soil.
Mycorrhizae associated with roots enhance nutrient absorption, and have been
responsible for the evolution of land plants.
2. Stems: stem fibers became stronger, being able to support stems & leaves in
the air = vascular system. The vascular system was an efficient transport system
for food, water & minerals.
The vascular system consists of 2 tissues: xylem and phloem
1) Xylem: carries water & minerals, consists of dead cells that form tubes.
2) Phloem: transports food, which was made in the leaves throughout the plant.
3. Leaves: primary organs for photosynthesis, allowing plants to make food more
efficiently.
Leaves consist of 2 adaptations: cuticle and stomata
1) Cuticle: secreted by epidermal cells & forms a waxy covering over the stem & leaves.
It helps to retain water & prevent drying out in the air.
2) Stomata: microscopic pores (singular "stoma") found in leaves & permit exchange of
gases.
4. Reproduction: methods of reproduction that are less dependent on water for
gamete dispersal.
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Land Plants Belong to One of 2 Divisions:
1) Nonvascular Plants: Bryophyta: (Mosses)
MOSSES: are the most familiar and the largest group of Bryophytes.
Habitat: Swampy &moist regions. They are low-growing clumps of cushiony, or green
velvety carpets. They have many adaptations to survive conditions on land.
Gametophyte Stage: dominant stage is a low-growing leafy plant with simple leaves,
stems & roots.
Stems &Leaves: have simple elongated cells to carry water, minerals & products of
photosynthesis. Each leaf is at the top of the stalk and absorbs water & minerals, and
performs photosynthesis.
Roots: called rhizoids anchor the plant.
Sporophyte Stage: diploid plant that has an elongated stalk that elevates the sporebearing capsule called the sporangium and provides more efficient arrangement for
scattering spores.
Sporangium: is the capsule where spores are produced by meiosis.
Ecological Role of Mosses: Mosses are pioneer plants, and establish themselves on
exposed rock or soil surfaces where there are no plants. They enrich the soil as they die
and build organic content that leads to soil formation. Mosses form peat (heating fuel),
they possess antiseptic properties (low pH), and they clean up oil spills.
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Reproduction: Life Cycle of a Moss:
Mosses have a life cycle that involves spores rather than seeds. Both sporophyte and
gametophyte stages exist on the same plant. Mosses undergo alternation of generations
(from haploid to diploid ….and diploid to haploid).
Sexual Reproduction of Moss Plants:, P. 259
1) Haploid spores (n) are produced by meiosis in the sporangium capsule (2n) and are
released into wind or water.
2) Protonema (n) forms after a spore germinates & undergoes mitosis, and resembles
a filamentous green algae.
3) The protonema (n) forms a small gametophyte plant consisting of root-like rhizoids,
shoots & green leaflets.
4) Mature gametophyte plant develops sex organs at its tip.
Antheridium = male sex organ, produces sperm cells (n).
Archegonium = female sex organ, produces eggs (n).
5) Fertilization occurs when plant is wet so sperm can swim to the egg (n + n) and a
zygote (2n) develops.
6) Zygote (2n) develops into a sporophyte plant (2n) consisting of a stalk &
sporangium.
Asexual Reproduction of Mosses:
1) fragmentation - parts breaking off the plant
2) gemmae - small, disk-like bodies made by gametophytes
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CLASSIFICATION OF LAND PLANTS:
2) Vascular Plants: Tracheophyta: (Ferns, Gymnosperms & Angiosperms)
All vascular plants except ferns are free of total dependence of water for reproduction.
Vascular tissue provides continuous internal conduction between roots, stems & leaves
and structural support.
Characteristics of Vascular Plants:, P. 261
1)
2)
3)
4)
5)
Multicellular
True Terrestrial Plants: Ferns, Conifers (gymnosperms) & Flowers (angiosperms)
Vascular System To Transport Nutrients
Dominant Sporophyte Generation
Gametophyte Stage Is Small & Dependent
Seedless Plants: Pterophyta: (Ferns)
FERNS: are the most familiar simple vascular plants. They are the most successful
seedless plants.
Habitat: they grow on bare, exposed rock in open bogs & marshes. Some ferns grow on
trees = epiphytes. Most prefer shady, moist habitats & they show the greatest diversity
in rainforests.
Sporophyte stage: is the dominant stage & it produces spores. Spores are produced in
clusters; called sori (singular "sorus") located on the lower surface of the frond.
Underground Stems: rhizomes
Roots: adventitious because they grow from rhizomes
Stems & roots: possess a primitive vascular system with tracheids
Leaves: called fronds consist of leaflets.
Gametophyte stage: starts as a prothallus and then exists as a heart-shaped plant.
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Ecological Role of Ferns: p. 263
Important as pioneer species, ferns establish themselves where no plants live & there is
very little soil (burned-over forests, barren areas, pastures, volcanic lava, land exposed
by retreat of glaciers). They improve living conditions for other species by creating soil &
preventing erosion until other plants take over. Ferns grown for food, "fiddleheads", are
young ferns are considered a delicacy, also used as decorations.
Reproduction: Life Cycle of a Fern:
The Life Cycle is primitive with separate sporophyte & gametophyte stages. Ferns
undergo alternation of generations (from haploid to diploid ….and diploid to haploid).
Asexual Reproduction of Ferns:
1) fragmentation - parts breaking off the plant
2) gametophyte - sometimes live independently with no sporophyte generation
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Sexual Reproduction of Fern Plants:,
1) Haploid spores (n) are produced by meiosis in the sporangium (2n) sori and are
released into the wind.
2) A prothallus forms after a spore germinates & undergoes mitosis. The prothallus is a
small, thin, green, heart-shaped gametophyte.
3) The prothallus (n) forms a small gametophyte heart-shaped plant consisting of rootlike rhizoids.
4) Mature gametophyte plant develops sex organs on the same plant (hermaphrodite).
Antheridium = male sex organ, produces sperm cells (n).
Archegonium = female sex organ, produces eggs (n).
5) Fertilization occurs when plant is wet so sperm can swim to the egg (n + n) and a
zygote (2n) develops.
6) Zygote (2n) develops into a sporophyte plant (2n) consisting of fiddleheads, fronds,
rhizomes and adventitious roots.
<Homework - Review Questions, p.263 (1-9)>
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Seed Plants: Conifers (Gymnosperms) & Flowering Plants (Angiosperms):
Seed plants are mostly free-living, some are parasitic.
Habitat: widely distributed, most prefer dry land, few prefer wetlands.
Size: varies from 1 mm to more than 100 m tall and are very complex.
Adaptations of Seed Plants: P.264
1) Reproductive adaptations: separate male & female gametophytes.
2) Produce seeds: each seed contains an embryo (2n) or partially developed plant.
3) Improved vascular system: helps move minerals, water, products of
photosynthesis
Two Types of Seed Plants:
1) Gymnosperms (Conifers): unprotected, naked seeds in cones.
2) Angiosperms (Flowering Plants): seeds are protected inside the fruit.
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1) Gymnosperms: Conifers: (Pines, spruces, junipers, firs, etc)
GYMNOSPERMS: are cone-bearing plants are widely distributed.
Habitat: they can live in harsh conditions (hot, dry & cold)
Leaves: are needlelike called needles. A hard, waxy cuticle covers the needles and helps
retain moisture.
Roots: extend over a wide surface area rather than penetrate deep into the soil, holds
the tree firm, even with little soil.
Seeds: are formed in cones and are not protected by the ovary wall. Gymnosperm
means "naked seed." Mature seeds are released from the cone and carried by the wind.
Ecological & Economic Role of Gymnosperms:
Balance level of gases (they remove co2). Felling large regions of forests for lumber is
upsetting balance. They provide food & shelter for animals. They control flooding by
absorbing water through their roots, & prevent erosion. The softwood lumber industry
is one of the biggest exports in Canada, with most of the wood going to the USA. Pine,
fir, spruce and cedar are all examples of conifers used around the world for building
homes, furniture, or almost anything else made with wood. They provide 80% of wood
for construction, furniture, & pulp & paper. They provide chemicals, such as: turpentine,
varnishes, disinfectants, fuels & medicines (epinephrine & taxol). Some are harvested to
the point of being endangered (California redwood & Newfoundland red pine).
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Life Cycle of Conifers: Alternation of Generations in Gymnosperms:
The life cycle is complex with a dominant sporophyte (2n) stage & a reduced
gametophyte. Pine trees produce two types of cones - male cones & female cones.
Sexual Reproduction of Gymnosperms (Conifers):, p. 266
1) Pollen grains (n) with wings, produced by meiosis in the male cone, are released into
the wind.
2) Pollen grains (n) land on the female cone, pollen is trapped in the sap & the pollen
tube grows toward the ovule.
3) Sperm is released from the pollen tube & unites with the egg to form a zygote (2n)
4) A year later, the zygote develops into an embryo (2n). The seed contains: an
embryo, a female gametophyte, & seed coat. Seeds are shed from the cone.
5) The seed develops into a seedling, which forms a mature sporophyte (2n), a tree.
6) The mature tree (sporophyte 2n) forms male cones (2n) at the bottom and
female cones (2n) at the top.
Other Gymnosperms: Cycads and ginkgoes are among the oldest, rarest, & most
unique. Cycads resemble palms, and are believed to have been the main nourishment
for herbiverous dinosaurs. Ginkgo is called a "living fossil", because it is the only species
of its division that has survived to present day. The trees have small flat leaves, and
produce seeds that look like fruit.
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2) Angiosperms: Flowering Plants: (Herbs, shrubs, trees, flowering plants)
ANGIOSPERMS: There are >250,000 species known & new ones are discovered daily;
these are the most diverse group of plants. Their success is due to the evolution of
insects. Insects could not survive without flowers = COEVOLUTION.
Habitat: they live in every type of climate.
Leaves: vary in shape, size, and thickness. A waxy cuticle covers the leaves and helps
retain moisture.
Roots: penetrate deep into the soil and hold the tree firm, like a tap root.
Seeds: are formed in fruits and are protected by the ovary wall which forms the fruit.
Flowers: vary in colour, shape, size, and odor.
The development of the flower, and therefore fruit, are key factors to the success of
angiosperms. These specialized structures create a symbiotic relationship with certain
animals to aid in fertilization and well as dispersion of the species. A flower attracts
insects or birds by scent and colour, and offers it sugary nectar for food. In exchange,
the animal is sprinkled with pollen to carry to the next flower for fertilization. After
fertilization, the flower will develop into a fruit, which may be harvested and eaten by
animals and may be carried for miles to be dropped with a bit of extra fertilizer.
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COMMON FLOWER STRUCTURES:
Stamen = Male Part of the Flower and Consists of:
1) Filament: thin stalk
2) Anther: structure where meiosis occurs and pollen grains are formed
Pistil = Carpel: Female Part of the Flower & Consists of:
1) Stigma: sticky part where pollen grains land and grow.
2) Style: slender stalk that leads from the stigma to the ovary.
3) Ovary: contains the ovule which is attached to the wall by a short stalk that was
formed by carpels. The ovule is where meiosis occurs and produces the embryo sac that
holds the egg cell (n) and endosperm cell (n+n).
Sepals: small, green leaf-like structures that surround the carpel and stamen.
Petals: colourful part of flowers that attract pollinators. At the base of the petals is
nectar.
Seed: fertilized ovule contains an embryonic plant & stored food.
Fruit: remaining structures of the ovary. Numerous seeds are found in fruits.
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Fruit develop from flowers. The fleshy part of the fruit develops from the ovary wall and
ovary of the flower. The function of this flesh varies in different plants, it nourishes,
protects, and aids in transport of the seeds. The fruit can take on a specialized shape to
be transported by wind (maple) or water (coconut), or can develop into a fruit that
offers an animal nutrition in exchange for transport. Many foods are fruits, such as
apples, bananas, oranges or melons, nuts, peas and beans, tomatoes, squash,
cucumber, and zucchini.
Ecological & Economic Role of Angiosperms:
Angiosperms play a major role for many animals by providing food, shelter, and
protection. For Humans, as with gymnosperms, angiosperms are important for lumber.
However, they generally have a different usage and are known as the hardwoods. Due
to their durability and strength, they are used for more expensive furniture and flooring.
Birch, maple, and oak are each examples of hardwoods that are commonly used for
these purposes.
When we think of angiosperms, we think of flowers and fruit, many parts of the plant
are consumed. For example, with sugar beets the root is used to make sugar, and with
sugar cane the stalk of the plant is used. We eat the roots of carrots, leaves of lettuce,
and stalk and flowers of broccoli. However, one group of fruits has an extremely large
effect on world nutrition. These are the grains. Wheat, corn and rice are consumed
worldwide as a base of consumption, providing starch to the diet.
Other uses of angiosperms are seen in drinks such as tea, coffee, cola or cocoa. Or in
clothing that is made of cotton. Rubber was derived from the rubber tree. One of the
largest plant markets, is the drug market. Opium, tobacco, cocaine and marijuana are all
examples of drugs that are derived from plants
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Life Cycle of Flowering Plants: Alternation of Generations in Angiosperms:
Life cycle is complex with a dominant sporophyte (2n) stage & reduced gametophyte.
Sexual Reproduction of Angiosperms (Flowers)
1) Pollen grains (n), produced by meiosis in the anther (2n), are dispersed by wind,
water, insects etc.
2) Pollination: pollen (n) lands on the sticky stigma (2n) and forms a pollen tube (n) that
grows down the style (2n) toward the ovule (n) in the ovary (2n).
3) The embryo sac (8 nuclei) is produced by meiosis, 3 nuclear divisions and
cytoplasmic divisions in the ovule, and is ready for the pollen tube.
4) The pollen tube reaches the ovule containing the embryo sac and releases 2 sperm.
5) Double fertilization occurs after 2 sperm are released & they unite with the egg cell
(n) & endosperm mother cell (n + n). A zygote (2n) & the triploid endosperm cell (3n)
are produced after fertilization. The zygote & triploid endosperm cell develop into
an embryo. The seed contains the embryo, endosperm, and the seed coat. Still
surrounding the seeds at this point is the fruit that has developed from the ovary
wall.
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Seed Dispersal: Two Advantages of Seed Dispersal:
1. Eliminates Competition
2. Increase Probability of Survival
*dispersal ensures plants do not drop under the parent plant
There are 4 Methods of Seed Dispersal:
1) Wind: small lightweight seeds can be carried great distances by winds (orchid,
poppies), fluffy parachute-like structures attached to seeds (dandelions, milkweed),
and wing-like structures attached to seeds (maple, sycamore, elm & ash).
2) Water: plants can use water to carry the seeds in streams and can move great
distances (water lilies, coconuts). These plants have air trapped in seed tissues &
fruit tissues so they can float (some for a year and still germinate).
3) Animals: excreting seeds ingested far from location of eating fruits, carrying seeds
with burrs, hooks, spines & stickers, allowing seeds to be carried from one place to
another on clothes, fur, feathers, and on the muddy feet of birds, ants & squirrels.
Squirrels bury acorns & other seeds while getting ready for hibernation.
4) Explosive "Mechanical Propulsion": plants have capsule fruits or pods that explode
when mature and propel the seed at some distance away from the parent.
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Pollination:
Various agents carry pollen to the stigma. Pollen grains are small grains containing the
male gametophyte and do not require water to fertilize to the egg. The pollen grain is
transported to the female gametophyte; the pollen tube grows toward the ovule and
releases the sperm.
THERE ARE SEVERAL METHODS OF DISPERSAL
1) Wind Dispersal: involves inconspicuous flowers (grasses, corn, wheat, trees,
poplars, walnuts, alders, birches, oaks, ragweed & sage). Flowers lack odor &
nectar. They are small and unattractive to insects. Pollen is lightweight, dry and
easily blown.
2) Insect Pollination: involves sweet smelling & brightly coloured flowers pollen is
carried on the bodies of insects and rubs off onto stigmas of other flowers that the
insect visits. Bees land on plants to gather nectar, moths, butterflies & humming
birds gather nectar while hovering. Moths will pollinate flowers at night.
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The Seed:
The seed consists of the embryo, endosperm, and seed coat.
Embryo development (2n): this begins while the ripened ovary or fruit is attached to the
plant. The growing embryo slowly forms root and shoot structures. In the monocot a
single seed leaf (cotyledon) develops and in the dicot two seed leaves (cotyledons) form.
Endosperm (3n): this is nutrient-rich food for the development of the new plant until
sufficient root hairs and chlorophyll for photosynthesis can sustain the plant.
Seed coat: called the testa protects the seed, and the seed may be dormant for many
years.
Germination: when conditions are optimal, the seed absorbs water & the seed coat
softens. The embryo begins to grow rapidly and the root and shoot break open the seed
coat. The root grows downward and the shoot grows upward and opens to expose the
cotyledons. The endosperm supports growth of the new plant.
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ANGIOSPERM DIVERSITY:
Flowering plants are grouped into 2 classes:
1) Monocotyledons (monocots)
2) Dicotyledons (dicots).
Cotyledon: seed leaf that stores food for the young sporophyte and becomes the first
leaf to appear as the seed germinates. Angiosperms are further classified into two
groups, the monocots and the dicots. This is based on their seed type and growth
pattern. The food portion of the seed is called the cotyledon, and as the name suggests,
a monocot has one cotyledon, and a dicot has two. Other differences are exemplified in
the table below.
Examples of Monocots: grasses, lilies, tulips, irises, crocuses, onions, orchids, crop
plants, wheat, corn, coconuts barley and rye.
Examples of Dicots: larger group of plants, maples, oaks, and cacti most forest trees and
a majority of flowering plants such as roses, fireweed, apples, cherries, and peaches.
<Homework - Review Questions, p. 274 (10-19)>
LAB: GERMINATION OF MONOCOT & DICOT SEEDS, P.275
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MERISTEMS:
Plant cells only divide in specific regions called meristems.
1) Apical meristems: are found in the root and shoot tips
2) Lateral meristems: increase plant's diameter
Primary Growth: In seed plants, root & shoot tissues begin to form in the embryo,
within the seed. As the seed germinates, cells at the root & shoot tip divide and
elongate. Lengthwise growth is called: primary growth. In young plants, evidence of
primary growth is seen when the green shoots emerge. Mature plants show primary
growth in the lengthening of their roots & stems. Due to the presence of meristems at
the roots and shoots, called apical meristems, primary growth occurs.
Secondary Growth: Many dicots and a few monocots exhibit secondary growth.
Secondary growth originates in tissues other than the root and shoot tips, but it results
in increases to the diameters of stems and roots. Due to the presence of meristems in
the trunk of the tree, called lateral meristems, secondary growth occurs.
<Homework - Review Questions, p.289 (1-5)>
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