16 lecture presentation

© 2010 Pearson Education, Inc.

COLONIZING LAND• Plants are terrestrial organisms that include forms that have

returned to water, such as water lilies.

Terrestrial Adaptations of Plants Structural Adaptations

• A plant is

– A multicellular eukaryote

– A photoautotroph, making organic molecules by photosynthesis



• In terrestrial habitats, the resources that a photosynthetic organism needs are found in two very different places:

– Light and carbon dioxide are mainly available in the air

– Water and mineral nutrients are found mainly in the soil


• The complex bodies of plants are specialized to take advantage of these two environments by having

– Aerial leaf-bearing organs called shoots

– Subterranean organs called roots

Reproductivestructures (such as

those in flowers)contain spores

and gametes

Leaf performsphotosynthesis

Cuticle reduces waterloss; stomata regulate

gas exchange

Shoot supports plant(and may perform

photosynthesis)

Surroundingwater supportsthe alga

Roots anchor plant;absorb water andminerals from thesoil (aided by fungi)

Whole algaperformsphotosynthesis;absorbs water,CO2, and

minerals fromthe water

Alga

Plant

Figure 16.1


• Most plants have mycorrhizae, symbiotic fungi associated with their roots, in which the fungi

– Absorb water and essential minerals from the soil

– Provide these materials to the plant

– Are nourished by sugars produced by the plant


• Leaves are the main photosynthetic organs of most plants, with

– Stomata for the exchange of carbon dioxide and oxygen with the atmosphere

– Vascular tissue for transporting vital materials

– A waxy cuticle surface that helps the plant retain water


• Two types of vascular tissue exist in plants:

– Xylem transports water and minerals from roots to leaves

– Phloem distributes sugars from leaves to the roots

Phloem

Xylem

Oak leaf

Vasculartissue

Figure 16.3


Reproductive Adaptations

• Plants produce their gametes in protective structures called gametangia, which have a jacket of protective cells surrounding a moist chamber where gametes can develop without dehydrating.


• The zygote develops into an embryo while still contained within the female parent in plants.

Embryo

Maternaltissue

LM

Figure 16.4


The Origin of Plants from Green Algae• The algal ancestors of plants

– Carpeted moist fringes of lakes or coastal salt marshes

– First evolved over 500 million years ago


• Charophytes

– Are a modern-day lineage of green algae

– May resemble one of these early plant ancestors

LM

LM

Figure 16.5


PLANT DIVERSITY• The history of the plant kingdom is a story of adaptation to

diverse terrestrial habitats.


Highlights of Plant Evolution• The fossil record chronicles four major periods of plant evolution.

Ancestralgreen algae

Origin of first terrestrial adaptations(about 475 mya)

Origin of vascular tissue(about 425 mya)

Origin of seeds(about 360 mya)

600 500 400 300 200 100 0

Origin of flowers(about 140 mya)

Millions of years ago

Angiosperms

Gymnosperms

Ferns and otherseedless vascularplants

Bryophytes

Charophytes (a groupof green algae) L

and

plan

ts

Vascu

lar plan

ts

Seed

plan

tsS

eedless

vascular

plan

ts

No

nvascu

larp

lants

(bryo

ph

ytes)

Figure 16.6


• (1) About 475 million years ago plants originated from an algal ancestor giving rise to bryophytes, nonvascular plants, including mosses, liverworts, and hornworts that are nonvascular plants without

– True roots

– True leaves


• (2) About 425 million years ago ferns evolved

– With vascular tissue

– But without seeds


• (3) About 360 million years ago gymnosperms evolved with seeds that consisted of an embryo packaged along with a store of food within a protective covering but not enclosed in any specialized chambers.

• Today, conifers, consisting mainly of cone-bearing trees such as pines, are the most diverse and widespread gymnosperms.

PLANT DIVERSITY

Bryophytes(nonvascular plants)

Ferns(seedless vascular plants)

Gymnosperms(naked-seed plants)

Angiosperms(flowering plants)

Figure 16.7


• (4) About 140 million years ago angiosperms evolved with complex reproductive structures called flowers that bear seeds within protective chambers called ovaries.


• The great majority of living plants

– Are angiosperms

– Include fruit and vegetable crops, grains, grasses, and most trees

Video: Flower Blooming (time lapse)


Bryophytes• Bryophytes, most commonly mosses

– Sprawl as low mats over acres of land

– Need water to reproduce because their sperm swim to reach eggs within the female gametangium

– Have two key terrestrial adaptations:

– A waxy cuticle that helps prevent dehydration

– The retention of developing embryos within the mother plant’s gametangium

Figure 16.8


• Mosses have two distinct forms:

– The gametophyte, which produces gametes

– The sporophyte, which produces spores

Spores

Spore capsule

Sporophyte

Gametophytes

Figure 16.9


• The life cycle of a moss exhibits an alternation of generations shifting between the gametophyte and sporophyte forms.

• Mosses and other bryophytes are unique in having the gametophyte as the larger, more obvious plant.

Blast Animation: Non-Flowering Plant Life Cycle

Animation: Moss Life Cycle

Blast Animation: Alternation of Generations

Gametes:sperm

and eggs(n)

Gametophyte(n)

Key

Haploid (n)

Diploid (2n)

osis

Mit

Figure 16.10-1

Gametes:sperm

and eggs(n)

Zygote(2n)

Gametophyte(n)

Key

Haploid (n)

Diploid (2n)

FERTILIZATION

osis

Mit

Figure 16.10-2

Sporecapsule

Gametes:sperm

and eggs(n)

Zygote(2n)

Gametophyte(n)

Sporophyte(2n)

Key

Haploid (n)

Diploid (2n)

FERTILIZATION

osis

Mit

toMi

sis

Figure 16.10-3

Spores(n)

Sporecapsule

Gametes:sperm

and eggs(n)

Zygote(2n)

Gametophyte(n)

Sporophyte(2n)

Key

Haploid (n)

Diploid (2n)

MEIOSIS FERTILIZATION

osis

Mit

toMi

sis

Figure 16.10-4

Spores(n)

Sporecapsule

Gametes:sperm

and eggs(n)

Zygote(2n)

Gametophyte(n)

Sporophyte(2n)

Key

Haploid (n)

Diploid (2n)

MEIOSIS FERTILIZATION

osis

Mitosis

Mit

toMi

sis

Figure 16.10-5


Ferns• Ferns are

– Seedless vascular plants

– By far the most diverse with more than 12,000 known species

• The sperm of ferns, like those of mosses

– Have flagella

– Must swim through a film of water to fertilize eggs

Animation: Fern Life Cycle

Spore capsule

“Fiddlehead”(young leaves

ready to unfurl)

Figure 16.11

Figure 16.11a

Figure 16.11b


Gymnosperms• At the end of the Carboniferous period, the climate turned drier

and colder, favoring the evolution of gymnosperms, which can

– Complete their life cycles on dry land

– Withstand long, harsh winters

• The descendants of early gymnosperms include the conifers, or cone-bearing plants.


Conifers

• Conifers

– Cover much of northern Eurasia and North America

– Are usually evergreens, which retain their leaves throughout the year

– Include the tallest, largest, and oldest organisms on Earth

Figure 16.13


Terrestrial Adaptations of Seed Plants

• Conifers and most other gymnosperms have three additional terrestrial adaptations:

– Further reduction of the gametophyte

– Pollen

– Seeds


• Seed plants have a greater development of the diploid sporophyte compared to the haploid gametophyte generation.


• A pine tree or other conifer is actually a sporophyte with tiny gametophytes living in cones.

Animation: Pine Life Cycle


• A second adaptation of seed plants to dry land was the evolution of pollen.

• A pollen grain

– Is actually the much-reduced male gametophyte

– Houses cells that will develop into sperm


• The third terrestrial adaptation was the development of the seed, consisting of

– A plant embryo

– A food supply packaged together within a protective coat


• Seeds

– Develop from structures called ovules, located on the scales of female cones in conifers

– Can remain dormant for long periods before they germinate, as the embryo emerges through the seed coat as a seedling


Angiosperms• Angiosperms

– Dominate the modern landscape

– Are represented by about 250,000 species

– Supply nearly all of our food and much of our fiber for textiles

• Their success is largely due to

– A more efficient water transport

– The evolution of the flower


Flowers, Fruits, and the Angiosperm Life Cycle

• Flowers help to attract pollinators who transfer pollen from the sperm-bearing organs of one flower to the egg-bearing organs of another.

Video: Bat Pollinating Agave Plant

Video: Bee Pollinating


• A flower has;

– Sepals

– Petals

– Stamens

– Carpels

Blast Animation: Flower Structure

Petal

CarpelStamen

SepalOvule

Anther

Filament

Stigma

Style

Ovary

Figure 16.17


• Flowers come in many forms.

Pansy Bleeding heart California poppy Water lily

Figure 16.18

Pansy

Figure 16.18a

Bleeding heart Figure 16.18b

Californiapoppy

Figure 16.18c

Water lily

Figure 16.18d


• Flowers are an essential element of the angiosperm life cycle.

Animation: Seed Development

Video: Flowering Plant Life Cycle (time lapse)

Animation: Plant Fertilization

Animation: Fruit Development

Blast Animation: Flowering Plant Life Cycle

Blast Animation: Pollination and Fertilization

Maturesporophyteplant withflowers

Sporophyteseedling

Germinatingseed

Seed

Seed (developsfrom ovule)

Fruit (developsfrom ovary)

Embryo(sporophyte)

Twospermnuclei

Zygote

EndospermEmbryo sac(femalegametophyte)

Egg

FERTILIZATION

Key

Haploid (n)

Diploid (2n)

Anther at tip of stamen

Pollen tube growingdown style of carpel

Ovary (base of carpel)Ovule

Germinated pollen grain(male gametophyte) onstigma of carpel

Figure 16.19-6


• Although both have seeds

– Angiosperms enclose the seed within an ovary

– Gymnosperms have naked seeds


• Fruit

– Is a ripened ovary

– Helps protect the seed

– Increases seed dispersal

– Is a major food source for animals

Winddispersal

Animaltransportation

Animalingestion

Figure 16.20

Winddispersal

Figure 16.20a

Animal transportation

Figure 16.20b

Animal ingestionFigure 16.20c


Angiosperms and Agriculture

• Gymnosperms supply most of our lumber and paper.

• Angiosperms

– Provide nearly all our food

– Supply fiber, medications, perfumes, and decoration


Plant Diversity as a Nonrenewable Resource• The exploding human population is

– Extinguishing plant species at an unprecedented rate

– Destroying fifty million acres, an area the size of the state of Washington, every year!

Figure 16.21


• Humans depend on plants for thousands of products including

– Food

– Building materials

– Medicines

Table 16.1


• Preserving plant diversity is important to many ecosystems and humans.

• Scientists are now rallying to

– Slow the loss of plant diversity

– Encourage management practices that use forests as resources without damaging them


FUNGI• Fungi

– Recycle vital chemical elements back to the environment in forms other organisms can assimilate

– Form mycorrhizae, fungus-root associations that help plants absorb from the soil

– Minerals

– Water


• Fungi are

– Eukaryotes

– Typically multicellular


• Fungi

– Come in many shapes and sizes

– Represent more than 100,000 species

Video: Water Mold Zoospores

Video: Water Mold Oogonium

Orange fungi

Mold

Predatory fungus

Budding yeastA “fairy ring”

Bud

Roundworm Body of fungus

Co

lori

zed

SE

M

Co

lori

zed

SE

MC

olo

rize

d S

EM

Figure 16.22


Characteristics of Fungi• Fungi have unique

– Structures

– Forms of nutrition


Fungal Nutrition

• Fungi

– Acquire their nutrients by absorption


• A fungus

– Digests food outside its body

– Secretes powerful digestive enzymes to break down the food

– Absorbs the simpler food compounds


Fungal Structure

• The bodies of most fungi are constructed of threadlike filaments called hyphae.

• Hyphae are minute threads of cytoplasm surrounded by a

– Plasma membrane


• Hyphae branch repeatedly, forming an interwoven network called a mycelium (plural, mycelia), the feeding structure of the fungus.

Animation: Fungal Reproduction and Nutrition

Reproductivestructure

MyceliumMycelium

Hyphae Spore-producingstructures

Figure 16.23

Mycelium

Spore-producingstructures

Reproductivestructure

Hyphae

Figure 16.23a


The Ecological Impact of Fungi• Fungi have

– An enormous ecological impact

– Many interactions with humans


Fungi as Decomposers

• Fungi and bacteria

– Are the principal decomposers of ecosystems

– Keep ecosystems stocked with the inorganic nutrients necessary for plant growth

• Without decomposers, carbon, nitrogen, and other elements would accumulate in nonliving organic matter.


Parasitic Fungi

• Parasitic fungi absorb nutrients from the cells or body fluids of living hosts.

• Of the 100,000 known species of fungi, about 30% make their living as parasites, including

– Dutch elm disease

– Deadly ergot, which infests grain

(a) American elm trees killed by Dutchelm disease fungus

Figure 16.24a

(b) ErgotsFigure 16.24b


• About 50 species of fungi are known to be parasitic in humans and other animals, causing

– Lung and vaginal yeast infections

– Athlete’s foot


Commercial Uses of Fungi

• Fungi are commercially important. Humans eat them and use them to

– Produce medicines such as penicillin

– Decompose wastes

– Produce bread, beer, wine, and cheeses

Truffles(the fungal kind, not the chocolates)

Blue cheese

Chanterellemushrooms

Figure 16.26

Truffles(the fungal kind,not the chocolates)

Figure 16.26a

Blue cheese

Figure 16.26b

Chanterellemushrooms

Figure 16.26c

Penicillium Zone of inhibited growth

Staphylococcus

Figure 16.27

16 lecture presentation

Science

pearson education

origin of plants

algal ancestors of plants

water alga plant figure

colonizing land plants

mother plants gametangium

complex bodies of plants

plant kingdom