Chapter 22 Plants with Seeds: Chapter 22 Plants with Seeds Charles Page High School
Dr. Stephen L. Cotton
Section 22-1 Seeds Plants - The Spermopsida: Section 22-1 Seeds Plants - The Spermopsida OBJECTIVES:
Describe several adaptations of seed plants to life on land.
Section 22-1 Seeds Plants - The Spermopsida: Section 22-1 Seeds Plants - The Spermopsida OBJECTIVES:
Identify the functions of roots, stems, and leaves.
Section 22-1 Seeds Plants - The Spermopsida: Section 22-1 Seeds Plants - The Spermopsida OBJECTIVES:
Explain why reproduction in seed plants is not dependent upon water.
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida Compared to life in water, life on land offers several benefits to plants
abundant sunlight
free movement of gaseous carbon dioxide and oxygen
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida But, life on land also presents significant problems to plants
water and nutrients available only from the soil
water is lost by evaporation
tissues upright to catch sun
reproduction without water
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida Seed plants are:
Kingdom Plantae
Phylum Tracheophyta- includes ferns and higher plants; these have true roots, stems, leaves
phylum Bryophyta - includes mosses, liverworts, and hornworts - page 450
subphylum Spermopsida
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida The Seed Plants have numerous adaptations that allow them to survive the difficulties of life on land
they did not evolve these adaptations because they “wanted” to
certain varieties were “fit”
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida Thus over time, seed plants evolved a variety of new adaptations that enabled them to survive in locations that mosses and ferns could not
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida The adaptations include:
well-developed vascular tissue
conducts water and nutrients between roots and leaves
roots, stems, leaves, and structures that enable them to live everywhere
from frigid mountains to scorching desert
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida and they developed seeds- a new form of sexual reproduction that does not require standing water
Just like in our bodies, plant cells are organized into different tissues and organs
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida The 3 main organs of a plant are roots, stems, and leaves- each with a special function
ROOTS- several functions
1. absorb water and dissolved nutrients from the soil
2. anchor plants in the ground
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida ROOTS - several functions:
3. hold plants upright, prevents them from bring knocked over by wind and rain
Roots also prevent soil from washing away, by holding soil particles together
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida STEMS:
hold a plant’s leaves up to the sun, often higher than other plants
plants compete with one another for solar energy
thus, stems must be very sturdy
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida LEAVES:
the organs in which plants capture the sun’s energy, a process vital to photosynthesis
may have broad surfaces over which to spread their chlorophyll and capture more energy
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida LEAVES:
these broad areas also expose a great deal of tissue to dry out
they are protected by a waxy coating called the cuticle
adjustable openings (called stomata) conserve water, and let gases such as oxygen and carbon dioxide in and out
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida As plants evolved longer stems, the distance between leaves and roots increased
water must travel this distance
compounds produced by the leaves must also travel down
Answer? A vascular system
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida Note Figure 22-3, page 469
The vascular system is a “two-way plumbing system”, made of two types of tissues
xylem and phloem
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida XYLEM-
a vascular tissue primarily responsible for carrying water and dissolved nutrients from roots to stems and leaves
often have thick walls
provide strength to the wood (wood is mainly xylem tissue)
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida Oddly enough, most xylem cells grow to maturity, and then die before they function as water carriers!
PHLOEM-
carries the products of photosynthesis (food)
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida PHLOEM-
xylem carries only upward
phloem carries materials either upward or downward
functioning phloem cells are alive, and filled with cytoplasm
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida Like other plants, seed plants have “alternation of generations”
Note Figure 21-12, page 459
However, the life cycles of seed plants are well-adapted for the rigors of life on land
probably the only plants in the desert!
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida All of the seed plants we see around us are in the sporophyte generation
the gametophyte generation of seed plants are tiny, consisting of only a few cells
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida Flowers and Cones -
the tiny gametophytes of seed plants grow and mature within the parts of the sporophyte we call flowers and cones
these are special reproductive structures
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida Because they develop within the sporophyte plant, neither the gametophytes nor gametes need standing water to function
thus, the flowers and cones are important adaptations that have contributed to the success to seed plants
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida Pollination -
the entire male gametophyte of seed plants is contained in a tiny structure called a pollen grain
sperm do not swim through water to fertilize the eggs
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida The structures that protect the zygotes of seed plants are seeds
the embryo, still inside the seed, stops growing while it is quite small
when it begins to grow again later, it uses a stored supply of food inside the seed
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida A seed coat surrounds the embryo and protects the food supply from drying out
thus, inside the seed coat, the embryo can remain dormant for long periods of cold, heat, or drought
Section 22-1 Seed Plants - The Spermopsida: Section 22-1 Seed Plants - The Spermopsida When conditions once again become favorable, the embryo can resume growth
Thus, seeds allow seed plants to survive and increase their numbers in a habitat where mosses and ferns cannot
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants OBJECTIVES:
Describe the evolution of seed plants.
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants OBJECTIVES:
List several characteristics of gymnosperms and angiosperms.
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants OBJECTIVES:
Compare monocots and dicots.
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants The history of plant evolution is marked by several great adaptive radiations
each time a group of plants evolved a useful new adaptation (such as vascular tissue or seeds), that group of plants gave rise to many new species
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Why? These new species were able to move into previously empty niches
Remember: the Earth’s environment did not remain constant- over millions of years, landmasses moved, mountain ranges moved, etc.
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Mosses and ferns, for example, underwent major adaptive radiation 300 to 400 million years ago, when land environments were much wetter than today
grew into lush forests that covered much of the Earth
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants But, as time went on, the continents became much drier
harder for spore-bearing plants to survive and reproduce
thus, many moss and fern species became extinct; replaced by seed plants equipped to deal with dryness
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants The first seed-bearing plants, which appeared during the Devonian period (285-345 million years ago- page 277), resembled ferns
called seed ferns, and reproduced by seeds rather than spores
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Although seed ferns were quite successful for a time, they were rapidly replaced by other plant species
today, no seed ferns survive
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants The most ancient surviving seed plants belong to 3 classes:
the Cycadae
the Ginkgoae
the Coniferae
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants In plants of these classes, a number of leaves have evolved into specialized male and female reproductive structures called scales
scales are grouped into larger structures called male and female cones
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Male cones produce male gametophytes called pollen
Female cones produce female gametophytes called eggs
later, the female cones hold seeds that develop on their scales
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Each seed is protected by a seed coat, but the seed is not covered by the cone
because their seeds sit “naked” on the scales, Cycads, Ginkgoes, and Conifers are called naked-seed plants, or Gymnosperms
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants CYCADS-
beautiful, palmlike plants
appeared during Triassic Period, 225 millions years ago
thrived when dinosaurs roamed the Earth
dinosaurs may have eaten them
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants CYCADS-
today, only 9 genera remain, including the oddly named sago palm (Fig. 22-7, p.472)
grow naturally in tropical and subtropical places such as Mexico, West Indes, Florida, parts of Asia, Africa, Australia
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants GINKGOES-
common when dinosaurs were alive
today, only 1 species remains (Ginkgo biloba) Fig. 22-8, p.472
looks almost like it’s fossil ancestors- a true “living fossil”
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants GINKGOES-
Ginkgo biloba may be the oldest seed plant species alive today
certainly among the earliest seed plants
Chinese have grown it in gardens for thousands of years
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Conifers- commonly called “evergreens”, are the most abundant gymnosperms today
pines, spruce, fir, cedar, sequoias, redwoods
some, such as the dawn redwood, date back 400 million years-well before the cycads
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Although other classes of gymnosperms are largely extinct, conifers still cover vast areas of North America, China, Europe, and Australia
some live more than 4,000 years, and can grow to more than 100 meters tall
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Adaptations of Conifers?
Leaves are long and thin, often called needles
evergreen name is misleading, because the needles do not remain on forever
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Some conifers will lose their needles every fall, such as larches and bald cypress
others may keep their needles for between 2 and 14 years
they seem “evergreen” because older needles drop off gradually all year long= never totally bare
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Reproduction?
Like other gymnosperms, most conifers produce two kinds of cones - Fig. 22-9, page 473
the scales that form these cones carry structures called sporangia, that produce male and female gametophytes
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Male cones, called pollen cones, produce male gametophytes in the form of pollen grains
Female cones, called seed cones, house the female gametophytes that produce ovules (eggs)
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Some species of conifers produce male and female cones on the same plant, whereas other species have separate male and female plants
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Each spring, pollen cones release millions of dustlike pollen grains carried by the wind
many fall to the ground or land in water, and are wasted
some drift onto seed cones (female cones), and are caught by sticky secretions
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants When a pollen grain lands near a female gametophyte, it produces sperm cells by mitosis
they then burst out of the pollen grain and fertilize ovules
seeds are produced, and may after a period of time, develop into new conifers
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Angiosperms- are flowering plants
reproduce sexually through their flowers, through a process of pollination
seeds are not carried naked on the flower parts, but in a protective structure- a fruit
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants The scientific term “fruit” not only refers to plant structures normally called fruits, but also refers to many things commonly called vegetables
apples, oranges, beans, pea pods, pumpkins, tomatoes, and eggplants are all fruits
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Today, angiosperms are the most widespread of all land plants
from frigid mountains to blazing deserts, from humid rain forests to temperate backyards near your home
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Some even live under water
they have evolved specialized tissues that allow them to survive extreme heat and cold, and well as long periods of drought
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Angiosperms separated into two subclasses:
Monocotyledonae, called monocots for short
Dicotyledonae, called dicots for short
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Monocots include:
corn, wheat, lilies, daffodils, orchids, and palms
Dicots include:
plants such as roses, clover, tomatoes, oaks, and daisies
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Several differences between monocots and dicots:
simplest difference is the number of leaves the embryo plant has when it first begins to grow, or germinate - these leaves are called cotyledons, or seed leaves
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Monocotyledons have one seed leaf (mono- means one)
Dicotyledons start off with two seed leaves (di- means two)
In some species, cotyledons are filled with food for the germinating plant; others have them as the first true leaves
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Note Fig. 22-12, page 475:
#1. Veins in monocot leaves usually lie parallel to one another; in dicots the leaves form a branching network
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Note Fig. 22-12, page 475:
#2. In monocot flowers, petals and other flower parts are usually found in threes or multiples of threes; in dicot flowers, petals and other flower parts are found in fours or fives, or multiples of fours or fives
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Note Fig. 22-12, page 475:
#3. In monocot stems, xylem and phloem tissues are gathered into vascular bundles scattered throughout the stem; in dicots, these vascular bundles are arranged in a ring near the outside of the stem
Dicots --> Monocots -->: Dicots --> Monocots -->
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Note Fig. 22-12, page 475:
#4. In monocot roots, bundles of xylem and phloem alternate with each other in a circular arrangement; in dicots, a single mass of xylem tissue forms an X in the center of the root, with phloem between the X arms
Section 22-2 Evolution of Seed Plants: Section 22-2 Evolution of Seed Plants Note Fig. 22-12, page 475:
#5. Most monocots have stems and roots that do not grow thicker from year to year (thus few tree-like monocots; palm is an exception); some dicots grow thicker year to year. Most flowering trees we see are dicots
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals OBJECTIVES:
Describe the process of pollination in seed plants.
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals OBJECTIVES:
Explain plant-animal coevolution.
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals OBJECTIVES:
Discuss the importance of seed dispersal to the success of the seed plants.
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals We have all seen insects and birds travel from flower to flower
We take for granted that flowers are brightly colored, or smell nice
We know fruits are tasty and nutritious, as well as colorful
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals But, how and why did insects begin exhibiting flower-visiting behavior?
The process by which two organisms evolve structures and behavior in response to each other over time is called coevolution
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals We can see this relationship between angiosperm flowers and a wide variety of animal species
Toward the end of the Cretaceous period (65 million years ago), Earth’s climate changed dramatically
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals Dinosaurs and many gymnosperms became extinct
This mass extinction opened up many niches for other organisms
new adaptive radiations of both plants and animals occurred
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals Pollination is essential to the reproduction of flowering plants
Over millions of years, a variety of ways to ensure that pollination will occur has evolved
Some use the wind: willow trees, ragweed, and grasses such as corn and wheat
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals Wind-pollinated plants usually have small, plain simple flowers with little or no fragrance
Most angiosperms are not pollinated by the wind
Most flowering plants are pollinated by insects, birds, or mammals that carry pollen
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals The plants in return provide the pollinators with food
the food may take the form of pollen, or a liquid called nectar, which may contain up to 25% glucose
or a combination of pollen and nectar
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals When a bee finds food on a particular flower, it remembers the color, shape, and odor- then search for more of the same type
while feeding, it might also pick up pollen- can be transferred to the next flower it visits (which will be the same species)
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals This interaction of plant-animal improves the evolutionary fitness of both
insects learn to identify good sources of food
plants benefit from efficient vector pollination (from animals); much better than just the wind
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals Of course, flowers that depend on specific animals for pollination evolved only after those animals evolved
Many plants have brightly colored flower petals that bees can see well
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals Because bees can see ultraviolet, blue, and yellow light the best, these are the colors of most bee-pollinated flowers
Flowers that are pollinated by bees usually have some kind of “landing platform” since they only gather while not flying
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals Flowers that have coevolved with animals other than bees show different methods of attracting pollinators
night flying moths cannot see color, but have an excellent sense of smell; thus color may be plain white, but fragrant
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals Moth-pollinated flowers usually do not have “landing platforms” because moths feed while hovering in midair
Several species of flowers are pollinated by flies that lay their eggs in the bodies of dead and decaying animals
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals These would not make good houseplants, because they would smell like rotting meat!
Fig. 22-17, page 479
Birds have a poor sense of smell, but a good sense of sight
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals Birds can easily see the colors of orange and red, and thus are attracted to these, but not to fragrant flowers
Just as flowers have different methods of pollination, angiosperm fruits have methods of scattering their seeds
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals The process of distributing seeds away from the parent plants is called seed dispersal
this is important to eliminate competition with the parent plant for sunlight, water, and nutrients
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals Seed dispersal also allows plants to colonize new environments
Several different methods are possible for seed dispersal
some are carried by the wind
Fig. 22-18, page 479
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals In other angiosperms, pressure builds inside the fruit and finally forces the seeds out of the ripe fruit like bullets from a gun
garden plant impatiens has fruits that spring open when touched, scattering the seeds over great distances
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals Some fruits have attractive colors, pleasant tastes, and contain a variety of nutritious compounds
they are eaten by animals; the fruit is digested, but not the seeds- they pass undamaged through the digestive system
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals Why are unripe fruits green and have a bitter taste?
If eaten too soon, the immature seeds will not grow
the bitter taste discourages animals from eating them if they are not ripe; green colors blend in with the green leaves
Section 22-3 Coevolution of Flowering Plants & Animals: Section 22-3 Coevolution of Flowering Plants & Animals When the fruits ripen, the color changes from the original green, and is more attractive
the bitter taste changes to a more sweet taste