agenda 2/7/11 chem warmup ap exam grade changes finish protista slides look at pond water while i...

Agenda 2/7/11

• Chem Warmup• AP Exam grade changes• Finish Protista slides• Look at pond water while I check Ch. 29 notes• Protista animations and practice we’ll do on Wed. in

computer lab

Homework – Incorporate Ch. 30 by Wed., and 31 by Fri.,32&33 by next Mon., 34 by next Wed.Test next Friday!!!!

Protista – making sense of it!! This is a paraphyletic kingdom

• Different ways of thinking about them:1) Based on nutrition:

animal-like (ingestive) = protozoa fungal-like (absorptive)

plant-like (photosynthetic) = algae 2) Based on phylogeny (how your packet is organized): Using similarities in cell structure, SSU-rRNA, life cycles, and

cytoskeletal proteinsSTILL VERY MUCH A WORK IN PROGRESS

• The kingdom Protista formed a paraphyletic group, with some members more closely related to animals, plants, or fungi than to other protists.

• Systematists have split the former kingdom Protista into as many as 20 separate kingdoms.

• Still,“protist” is used as an informal term for this great diversity of eukaryotic kingdoms.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 28.2

• What’s a mixotroph?

• What is plankton? Phytoplankton?

• Can Protists be symbionts?

Explain this figure!!

• Each endosymbiotic event adds a membrane derived from the vacuole membrane of the host cell that engulfed the endosymbiont.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin CummingsFig. 28.5

• Photosynthetic protists have evolved in several clades that also have heterotrophic members.

• Different episodes of secondary endosymbiosis account for the diversity of protists with plastids.


Fig. 28.25

• The conventional model of relationships among the three domains place the archaea as more closely related to eukaryotes than they are to prokaryotes.– Similarities include proteins

involved in transcription and translation.

– This model places the host cell in the endosymbiotic origin of eukaryotes as resembling an early archaean.


Fig. 28.6

• All three domains seem to have genomes that are chimeric mixes of DNA that was transferred across the boundaries of the domains.

• This has lead some researchers to suggest replacing the classical tree with a web-like phylogeny


Fig. 28.7


And who’s not on here?

Let’s be sure your packet is complete!

Why grouped this way? Be sure you addressed this in your notes?

Not so important to memorize as it is to see why classified as they are.

Match the Protist with it’s description and identify it’s taxons/clades as applicable1) Blooms cause red tides2) Causes potato blight3) Causes an STD4) Has a red eyespot5) Kelp6) Moves with pseudopodia7) Sushi wraps8) 2 part glass-like silica walls9) Causes malaria10) Causes “hiker’s diarrhea”11) Closest relatives of land

plants12) Causes sleeping sickness13) Algae with yellow and

brown pigments14) Convergent evolution to

fungi15) Has micro and macronuclei

A) Slime moldB) DiatomsC) Oomycetes (water molds,etc.)D) Red algaeE) Brown algaeF) Golden algaeG) DinoflagellatesH) EuglenaI) Ciliate like ParameciumJ) Trypanosoma sp.K) Trichomonas vaginalisL) Giardia intestinalisM) PlasmodiumN) AmoebaO) Green algae

Which 3 of these have seaweed members?

Agenda 2/8/11

• Everyone see pond critters? What kinds?• Go over matching Protista activity• Start How Plants Colonized Land – to Vascular

Plants

Homework – Incorporate Ch. 30 by Wed., and 31 by Fri.,

32&33 by next Mon., 34 by next Wed.

Test next Friday!!!!

Plants move onto land

• Advantages increased sunlight unfiltered by water, more carbon dioxide in the atmosphere than in water, soils rich in nutrients, and fewer predators/pathogens at first.

• Challenges lack of water, dessication, and a lack of structural support against gravity

• Changed Earth for the rest of us – oxygen, food

• There are four main groups of land plants: bryophytes, pteridophytes, gymnosperms, and angiosperms.

• The most common bryophytes are mosses.

• The pteridophytes include ferns.• The gymnosperms include pines and

other conifers.• The angiosperms are the flowering plants.

Evolutionary adaptations to terrestrial living characterize the four main groups of land plants



Fig. 29.1

1) Both possess rosette cellulose-synthesizing complexes (vs. linear in other algae) that synthesize the cellulose microfibrils of the cell wall.

2) Both have peroxisomes with enzymes that help minimize loss of organic products due to photorespiration.

3) Structure of their sperm closely related

4) Produce cell plate in cell division alike,

includes the formation of a phragmoplast, an alignment of cytoskeletal elements and vesicles

5) Similarity between nuclear and chloroplast genes

Charophyceans are the green algae most closely related to land plants

• Several characteristics separate the four land plant groups from their closest algal relatives, including:– apical meristems (localized regions of cell

division at the tips of shoots and roots)– multicellular embryos dependent on the

parent plant– alternation of generations– sporangia that produce walled spores– gametangia that produce gametes

Several terrestrial adaptations distinguish land plants from charophycean algae


• In terrestrial habitats, the resources that a photosynthetic organism requires are found in two different places.– Light and carbon dioxide are mainly

aboveground.– Water and mineral resources are found mainly

in the soil.

• Therefore, plants show varying degrees of structural specialization for subterranean and aerial organs - roots and shoots in most plants.


• Multicellular plant embryos develop from zygotes that are retained within tissues of the female parent.

• The parent provides nutrients, such as sugars and amino acids, to the embryo.

• This distinction is the basis for a term for all land plants, embryophytes.

Fig. 29.4

• All land plants show alternation of generations in which two multicellular body forms alternate.– This life cycle also occurs in various algae.– However, alternation of generation does not

occur in the charophyceans, the algae most closely related to land plants.


• One of the multicellular bodies is called the gametophyte with haploid cells.– Gametophytes produce gametes, egg and

sperm.– Fusion of egg and

sperm duringfertilizationform a diploidzygote.


Fig. 29.6

•spore is a reproductive cell that can develop into a new organism without fusing with another cell.

• Unlike the life cycles of other sexually producing organisms, alternation of generations in land plants (and some algae) results in both haploid and diploid stages that exist as multicellular bodies.– For example, humans do not have alternation

of generations because the only haploid stage in the life cycle is the gamete, which is single-celled.


• The relative size and complexity of the sporophyte and gametophyte depend on the plant group.– In bryophytes, the gametophyte is the

“dominant” generation, larger and more conspicuous than the sporophyte.

– In pteridophytes, gymnosperms, and angiosperms, the sporophyte is the dominant generation.

• For example, the fern plant that we typically see is the diploid sporophyte, while the gametophyte is a tiny plant on the forest floor.

• Plant spores are haploid reproductive cells that grow into a gametophyte by mitosis.– Spores are covered by a polymer called

sporopollenin, the most durable organic material known.

– This makes the walls of spores very tough and resistant to harshenvironments.


Fig. 29.7

• Multicellular organs, called sporangia, are found on the sporophyte and produce these spores.

• Within a sporangia, diploid spore mother cells undergo meiosis and generate haploid spores.

• The outer tissues of the sporangium protect the developing spores until they are ready to be released into the air.


Fig. 29.8

• The gametophytes of bryophytes, pteridophytes, and gymnosperms produce their gametes within multicellular organs, called gametangia.

• A female gametangium, called an archegonium, produces a single egg cell in a vase-shaped organ.– The egg is retained

within the base.


Fig. 29.9a

• Male gametangia, called antheridia, produce many sperm cells that are released to the environment.– The sperm cells of bryophytes, pteridophytes,

and some gymnosperms have flagella and swim to eggs.

• A sperm fuses with an egg within an archegonium and the zygote then begins development into an embryo.


Fig. 29.9b

• Most land plants have additional terrestrial adaptations including:– adaptations for acquiring, transporting, and

conserving water, (water-proof cuticle, stomata that open and close, xylem and phloem)

– adaptations for reducing the harmful effect of UV radiation (Flavonoids absorb harmful UV radiation),

– adaptations for repelling terrestrial herbivores and resisting pathogens (secondary compounds such as alkaloids, terpenes, tannins, and phenolics with bitter tastes, strong odors, or toxic effects that help defend land plants against herbivorous animals or microbial attack.)

– Lignin, a phenolic polymer, hardens the cell walls of “woody” tissues in vascular plants, providing support for even the tallest of treesCopyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• The advanced charophyceans Chara and Coleochaeta are haploid organisms.– They lack a multicellular sporophyte, but the zygotes

are retained and nourished on the parent.

• The zygote of a charophyceans undergoes meiosis to produce haploid spores, while the zygote of a land plants undergoes mitosis to produce a multicellular sporophyte.– The sporophyte then produces haploid spores by

meiosis.

Alternation of generations in plants may have originated by delayed meiosis


• A reasonable hypotheses for the origin of sporophytes is a mutation that delayed meiosis until one or more mitotic divisions of the zygote had occurred.– This multicellular, diploid sporophyte would have

more cells available for meiosis, increasing the number of spores produced per zygote.


Fig. 29.13

• Many charophycean algae inhabit shallow waters at the edges of ponds and lakes where they experience occasional drying.– A layer of sporopollenin prevents exposed

charophycean zygotes from drying out until they are in water again.

– This chemical adaptation may have been the precursor to the tough spore walls that are so important to the survival of terrestrial plants.

Adaptations to shallow water preadapted plants for living on land


• The diversity of modern plants demonstrates the problems and opportunities facing organisms that began living on land.

• Because the plant kingdom is monophyletic, the differences in life cycles among land plants can be interpreted as special reproductive adaptations as the various plant phyla diversified from the first plants.

The plant kingdom is monophyletic


• Bryophytes are represented by three phyla:– phylum Hepatophyta - liverworts– phylum Anthocerophyta - hornworts– phylum Bryophyta - mosses

• Note, the name Bryophyta refers only to one phylum, but the informal term bryophyte refers to all nonvascular plants (no

xylem or phloem tissue)

which accounts for small size.

The three phyla of bryophytes are mosses, liverworts, and hornworts

• The diverse bryophytes are not a monophyletic group.– Several lines of evidence indicate that these

three phyla diverged independently early in plant evolution, before the origin of vascular plants. So they may not share a common ancestor.

• Liverworts and hornworts may be the most reasonable models of what early plants were like.

• Mosses are the bryophytes most closely related to vascular plants.


• In bryophytes, gametophytes are the most conspicuous, dominant phase of the life cycle.– Sporophytes are smaller and present only part of the

time.

• Bryophyte spores germinate in favorable habitats and grow into gametophytes by mitosis.

• The gametophyte is a mass of green, branched, one-cell-thick filaments, called a protonema.

The gametophyte is the dominant generation in the life cycles of bryophytes


• When sufficient resources are available, a protonema produces meristems.

• These meristems generate gamete-producing structures, the gametophores.


Fig. 29.16

Require water for sperm to swim to the egg during fertilization.

• The gametophytes of hornworts and some liverworts are flattened and grow close to the ground.


Fig. 29.15a, b, c

• While the bryophyte sporophyte does have photosynthetic plastids, they cannot live apart from the maternal gametophyte.

• A bryophyte sporophyte remains attached to its parental gametophyte throughout the sporophyte’s lifetime.– It depends on the gametophyte for sugars,

amino acids, minerals and water.

• Bryophytes have the smallest and simplest sporophytes of all modern plant groups.

Bryophyte sporophytes disperse enormous numbers of spores


• They are common and diverse in moist forests and wetlands.

• Some even inhabit extreme environments like mountaintops, tundra, and deserts.– Mosses can lose most of their body water

and then rehydrate and reactivate their cells when moisture again becomes available.

• Sphagnum, a wetland moss, is especially abundant and widespread.– It forms extensive deposits of undecayed

organic material, called peat.

Bryophytes provide many ecological and economic benefits


• Peatlands play an important role as carbon reservoirs, stabilizing atmospheric carbon dioxide levels.

• Sphagnum has been used in the past as diapers and a natural antiseptic material for wounds.

• Today, it is harvested for use as a soil conditioner and for packing plants roots because of the water storage capacity of its large, dead cells.


• Bryophytes were probably Earth’s only plants for the first 100 million years that terrestrial communities existed.– Then vegetation began to take on a taller

profile with the evolution of vascular plants.


• Modern vascular plants (pteridophytes, gymnosperms, and angiosperms) have food transport tissues (phloem) and water conducting tissues (xylem) with lignified cells.

• In vascular plants the branched sporophyte is dominant and is independent of the parent gametophyte.

• The first vascular plants, pteridophytes, were seedless.

Introduction to Vascular Plants


• Vascular plants built on the tissue-producing meristems, gametangia, embryos and sporophytes, stomata, cuticles, and sproropollenin-walled spores that they inherited from mosslike ancestors.

Additional terrestrial adaptations evolved as vascular plants

descended from mosslike ancestors


• Cooksonia, an extinct plant over 400 million years old, is the earliest known vascular plant.– Its fossils are found in Europe and North

America.– The branched sporophytes

were up to 50cm tall with small lignified cells, much like the xylem cells of modern pteridophytes.

A diversity of vascular plants evolved over 400 million years ago


Fig. 29.20

• The seedless vascular plants, the pteridophytes consists of two modern phyla:– phylum Lycophyta - lycophytes– phylum Pterophyta - ferns, whisk ferns, and

horsetails• These phyla probably

evolved from different ancestors among the early vascular plants.

Introduction to Pteridophytes


Fig. 29.21

• Most pteridophytes have true roots with lignified vascular tissue.

• These roots appear to have evolved from the lowermost, subterranean portions of stems of ancient vascular plants.– It is still uncertain if the roots of seed plants

arose independently or are homologous to pteridophyte roots.

Pteridophytes provide clues to the evolution of roots and leaves


• Lycophytes have small leaves with only a single unbranched vein.– These leaves, called microphylls, probably

evolved from tissue flaps on the surface of stems.

– Vascular tissue then grew into the flaps.


Fig. 29.24a

• From the early vascular plants to the modern vascular plants, the sporophyte generation is the larger and more complex plant.– For example, the leafy fern plants that you are

familiar with are sporophytes.– The gametophytes are tiny plants that grow

on or just below the soil surface.– This reduction in the size of the gametophytes

is even more extreme in seed plants.

A sporophyte-dominant life cycle evolved in seedless vascular plants


• Ferns also demonstrate a key variation among vascular plants: the distinction between homosporous and heterosporous plants.

• A homosporous sporophyte produces a single type of spore.– This spore develops into a bisexual

gametophyte with both archegonia (female sex organs) and antheridia (male sex organs).



Fig. 29.23

• A heterosporous sporophyte produces two kinds of spores.– Megaspores develop into females

gametophytes.– Microspores develop into male

gametophytes.

• Regardless of origin, the flagellated sperm cells of ferns, other seedless vascular plants, and even some seed plants must swim in a film of water to reach eggs.

• Because of this, seedless vascular plants are most common in relatively damp habitats.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• Phylum Lycophyta - Modern lycophytes are relics of a far more eminent past.– By the Carboniferous period, lycophytes

existed as either small, herbaceous plants or as giant woody trees with diameters of over 2m and heights over 40m.

– The giant lycophytes thrived in warm, moist swamps, but became extinct when the climate became cooler and drier.

– The smaller lycophytes survived and are represented by about 1,000 species today.

Lycophyta and Pterophyta are the two phyla of modern seedless vascular plants


• Modern lycophytes include tropical species that grow on trees as epiphytes, using the trees as substrates, not as hosts.

• Others grow on the forest floor in temperate regions.

• The lycophyte sporophytes are characterized by upright stems with many microphylls and horizontal stems along the ground surface.

• Roots extend down from the horizontal stems.


• The phylum Pterophyta consists of ferns and their relatives.

• Psilophytes, the whisk ferns, used to be considered a “living fossil”.

• Their dichotomous branching and lack of true leaves and roots seemed similar to early vascular plants.

• However, comparisons of DNA sequences and ultrastructural details, indicate that the lack of true roots and leaves evolved secondarily.


Fig. 29.21b

• Sphenophytes are commonly called horsetails because of their often brushy appearance.

• During the Carboniferous, sphenophytes grew to 15m, but today they survive as about 15 species in a single wide-spread genus, Equisetum.

• Horsetails are often found in marshy habitats and along streams and sandy roadways.


Fig. 29.21c

• Roots develop from horizontal rhizomes that extend along the ground.

• Upright green stems, the major site of photosynthesis, also produce tiny leaves or branches at joints.– Horsetail stems have a large air canal to allow

movement of oxygen into the rhizomes and roots, which are often in low-oxygen soils.

• Reproductive stems produce cones at their tips.– These cones consist of clusters of

sporophylls.• Sporophylls produce sporangia with haploid

spores.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• Ferns first appeared in the Devonian and have radiated extensively until there are over 12,000 species today. – Ferns are most diverse in the tropics but are

also found in temperate forests and even arid habitats.

• Ferns often have horizontal rhizomes from which grow large megaphyllous leaves with an extensively branched vascular system.– Fern leaves or fronds

may be divided into many leaflets.


Fig. 29.21d

• Ferns produce clusters of sporangia, called sori, on the back of green leaves (sporophylls) or on special, non-green leaves. http://www.youtube.com/watch?v=5hGQcmM6njY– Sori can be arranged in various patterns that are useful

in fern identification.– Most fern sporangia have springlike devices that

catapult spores several meters from the parent plant.– Spores can be carried great distances by the wind.


Fig. 29.24a, b

http://www.youtube.com/watch?v=5hGQcmM6njY



• The phyla Lycophyta and Pterophyta formed forests during the Carboniferous period about 290-360 million years ago.

• These plants left not only living represent-atives and fossils, but also fossil fuel in the form of coal.

Seedless vascular plants formed vast “coal forests” during the Carboniferous period


Fig. 29.25

• While coal formed during several geologic periods, the most extensive beds of coal were deposited during the Carboniferous period, when most of the continents were flooded by shallow swamps.

• Dead plants did not completely decay in the stagnant waters, but accumulated as peat.

• The swamps and their organic matter were later covered by marine sediments.

• Heat and pressure gradually converted peat to coal, a “fossil fuel”.


Agenda 2/9/11

• Finish Pteridophytes• To computer lab and do Campbell Biology

practice for Ch. 27, 28 and 29• I will check your Ch. 30 notes while we are there

Homework –Ch. 31 organizer by Fri.32 organizer and & 33 flashcards by next Mon.34 flashcards by next Wed.Test next Friday!!!!

Agenda 2/10/11

• Seed plants- Gymnosperms and Angiosperms• Watch Animation 6-3-2 parts 5 & 6• Practice Quiz• Start Fungi with Animation 6-3-4 starting with Overview

Homework- Ch. 31 organizer by Fri.32 organizer and & 33 flashcards by next Mon.34 flashcards by next Wed.Test next Friday!!!!

5 crucial adaptations led to the success of seed plants:

1) Reduced gametophytes

2) Heterospory

3) Ovules and the production of eggs

4) Pollen and the production of sperm

5) Seeds!

Reduction of Gametophyte – protects the delicate antheridia and archegonia,

increasing reprod. success• Male gametophytes = pollen grains• Female gametophyte produces eggs

• The seed represents a different solution to resisting harsh environments and dispersing offspring.– In contrast to a single-celled spore, a

multicellular seed is a more complex, resistant structure.

• A seed consists of a sporophyte embryo packaged along with a food supply within a protective coat.


The Seed Solution

• All seed plants are heterosporous, producing two different types of sporangia that produce two types of spores.– Megasporangia produce megaspores, which

give rise to female (egg-containing) gametophytes.• Microsporangia produce microspores, which give

rise to male (sperm-containing) gametophytes.

• In contrast to heterosporous seedless vascular plants, the megaspores and the female gametophytes of seed plants are retained by the parent sporophyte.

• Layers of sporophyte tissues, integuments, envelop and protect the megasporangium.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• An ovule consists of integuments, megaspore, and megasporangium.– A female gametophyte develops inside a megaspore

and produces one or more egg cells.– A fertilized egg develops into a sporophyte embryo.– The whole ovule develops into a seed.


Ovules and the production of Eggs

• A seed’s protective coat is derived from the integuments of the ovule.

• Within this seed coat, a seed may remain dormant for days, months, or even years until favorable conditions trigger germination.

• When the seed is eventually released from the parent plant, it may be close to the parent, or be carried off by wind or animals.


• The microspores, released from the microsporangium, develop into pollen grains.

• These are covered with a tough coat containing sporopollenin.

• They are carried away by wind or animals until pollination occurs when they land in the vicinity of an ovule.

• So, do seed plant sperm need flagella?

Pollen eliminated the liquid-water requirement for fertilization


• The climate had dried out, so gymnosperms became the dominant plant organisms instead of the ferns & lycophytes of the Carboniferous period

• Gymnosperms have “naked” seeds not enclosed in ovaries – they are on sporophylls (modified leaves) of cones

- vs. Angiosperm seeds are enclosed in fruits/mature ovaries

The Mesozoic era was the age of gymnosperms


• There are four plant phyla grouped as gymnosperms.

The four phyla of extant gymnosperms are ginko, cycads, gnetophytes, and conifers


Fig. 30.4

• Phylum Ginkgophyta consists of only a single extant species, Ginkgo biloba.– This popular ornamental species has fanlike leaves

that turn gold before they fall off in the autumn.– Landscapers usually only plant male trees because the

seed coats on female plants decay, they produce a repulsive odor (to humans, at least).


Fig. 30.5

• Cycads (phylum Cycadophyta) superficially resemble palms.– Palms are actually flowering plants.


Fig. 30.6

• Phylum Gnetophyta consists of three very different genera.– Weltwitschia plants, from deserts in

southwestern Africa, have straplike leaves.– Gentum species are tropical trees or vines.– Ephedra (Mormon tea) is a shrub of the

American deserts.


Fig. 30.7

• The conifers, phylum Coniferophyta, is the largest gymnosperm phylum.– The term conifer comes from the reproductive

structure, the cone, which is a cluster of scalelike sporophylls.

– Although there are only about 550 species of conifers, a few species dominate vast forested regions in the Northern Hemisphere where the growing season is short.


• Conifers include pines, firs, spruces, larches, yews, junipers, cedars, cypresses, and redwoods.


Fig. 30.8

• Angiosperms, better known as flowering plants, are vascular seed plants that produce flowers and fruits.

• They are by far the most diverse and geographically widespread of all plants.

• There are abut 250,000 known species of angiosperms, 90% of all plant species.

Angiosperms


• All angiosperms are placed in a single phylum, the phylum Anthophyta.

• As late as the 1990s, most plant taxonomists divided the angiosperms into two main classes, the monocots and the dicots.– Most monocots have leaves with parallel veins,

one cotyledon in the seed, and flowering parts in multiples of 3’s. Cotyledon=seed leaf

– Most dicots have netlike venation, 2 cotyledons in the seed, and flowering parts in multiples of 4’s and 5’s.

1. Systematists are identifying the angiosperm clades


• While most angiosperms belong to either the monocots (65,000 species) or eudicots (165,000 species) several other clades branched off before these.

• Based onmolecularanalyses,Arborellais the onlysurvivor ofa branch atthe base ofthe angio-sperm tree.


• While evolutionary refinements of the vascular system contributed to the success of angiosperms, the reproductive adaptations associated with flowers and fruits contributed the most.

• The flower is an angiosperm structure specialized for reproduction.– In many species, insects and other animals transfer

pollen from one flower to female sex organs of another.– Some species that occur in dense populations, like

grasses, rely on the more random mechanism of wind pollination.

The flower is the defining reproductive adaptation of angiosperms


• A flower is a specialized shoot with four circles of modified leaves: sepals, petals, stamens, and carpals.


Fig. 30.13a

• The sepals at the base of the flower are modified leaves that enclose the flower before it opens.

• The petals lie inside the ring of sepals.– These are often brightly colored in plant

species that are pollinated by animals.– They typically lack bright coloration in wind-

pollinated plant species.

• Neither the sepals or petals are directly involved in reproduction.


• Stamens, the male reproductive organs, are the sporophylls that produce microspores that will give rise to gametophytes.– A stamen consists of a stalk (the filament) and a

terminal sac (the anther) where pollen is produced.

• Carpals are female sporophylls that produce megaspores and their products, female gametophytes.– At the tip of the carpal is a sticky stigma that receives

pollen.– A style leads to the ovary at the base of the carpal.– Ovules and, later, seeds are protected within the ovary.


• A fruit is a mature ovary.– As seeds develop from ovules after fertilization,

the wall of the ovary thickens to form the fruit.– Fruits protect dormant seeds and aid in their

dispersal.

Fruits help disperse the seeds of angiosperms


Fig. 30.15

• Various modifications in fruits help disperse seeds.

• In some plants, such as dandelions and maples, the fruit functions like a kite or propeller, enhancing wind dispersal.

• Many angiosperms use animals to carry seeds.– Fruits may be modified

as burrs that cling to animal fur.

– Edible fruits are eaten by animals when ripe and the seeds are deposited unharmed, along with fertilizer. Fig. 30.16

• The fruit develops after pollination triggers hormonal changes that cause ovarian growth.– The wall of the ovary becomes the pericarp,

the thickened wall of the fruit.– The other parts of the flower whither away in

many plants.– If a flower has not been pollinated, the fruit

usually does not develop, and the entire flower withers and falls away.


• Fruits are classified into several types depending on their developmental origin.– Simple fruits are derived from a single ovary.

• These may be fleshy, such as a cherry, or dry, such as a soybean pod.

– An aggregate fruit, such as a blackberry, results from a single flower with several carpals.

– A multiple fruit, such as a pineapple, develops from an inflorescence, a tightly clustered group of flowers.


• By selectively breeding plants, humans have capitalized on the production of edible fruits.– Apples, oranges, and other fruits in grocery

stores are exaggerated versions of much smaller natural varieties of fleshy fruits.

• The staple foods for humans are the dry, wind-dispersed fruits of grasses.– These are harvested while still on the parent

plant.– The cereal grains of wheat, rice, corn, and

other grasses are actually fruits with a dry pericarp that adheres tightly to the seed coat of the single seed inside.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• All angiosperms are heterosporous, producing microspores that form male gametophytes and megaspores that form female gametophytes.– The immature male gametophytes are contained within

pollen grains and develop within the anthers of stamens.• Each pollen grain has two haploid cells.

– Ovules, which develop in the ovary, contain the female gametophyte, the embryo sac.• It consists of only a few cells, one of which is the egg.

The life cycle of an angiosperm is a highly refined version of the alternation of

generations common in plants


• The life cycle of an angiosperm begins with the formation of a mature flower on a sporophyte plant and culminates in a germinating seed.


Fig. 30.17

(1) The anthers of the flower produce (2) microspores that form (3) male gametophytes (pollen).

(4) Ovules produce megaspores that form (5) female gametophytes (embryo sacs).

(6) After its release from the anther, pollen is carried to the sticky stigma of a carpal.– Although some flowers self-pollinate, most have

mechanisms that ensure cross-pollination, transferring pollen from flowers of one plant to flowers of another plant of the same species.

– The pollen grain germinates (begins growing) from the stigma toward the ovary.


• When the pollen tube reaches the micropyle, a pore in the integuments of the ovule, it discharges two sperm cells into the female gametophyte.

(7) In a process known as double fertilization, one sperm unites with the egg to form a diploid zygote and the other fuses with two nuclei in the large center cell of the female gametophyte.

(8) The zygote develops into a sporophyte embryo packaged with food and surrounded by a seed coat.– The embryo has a rudimentary root and one or two seed

leaves, the cotyledons.• Monocots have one seed leaf and dicots have two.


• The seed consists of the embryo, endosperm, sporangium, and a seed coat from the integuments.

• As the ovules develop into seeds, the ovary develops into a fruit.

• After dispersal by wind or animals, a seed germinates if environmental conditions are favorable.– During germination, the seed coat ruptures and

the embryo emerges as a seedling.– It initially uses the food stored in the endosperm

and cotyledons to support development.


• Earth’s landscape changed dramatically with the origin and radiation of flowering plants.

• The oldest angiosperm fossils are found in rocks in the early Cretaceous, about 130 million years ago.

• By the end of the Cretaceous, 65 million years ago, angiosperms had become the dominant plants on Earth.

The radiation of angiosperms marks the transition from the

Mesozoic era to the Cenozoic era


• Coevolution• Some plants evolve to escape being eaten, some benefit• Plant-pollinator mutualism

Angiosperms and animals have shaped one another’s evolution


• Flowering plants provide nearly all our food.– All of our fruit and vegetable crops are

angiosperms.– Corn, rice, wheat, and other grain are grass

fruits.• The endosperm of the grain seeds is the main food

source for most of the people of the world and their domesticated animals.

• We also grow angiosperms for fiber, medications, perfumes, and decoration.

Agriculture is based almost entirely on angiosperms


• The demand for space and natural resources resulting from the exploding human population is extinguishing plant species at an unprecedented rate.

• This is especially acute in the tropics where half the human population lives and where growth rates are highest.– Due primarily to the slash-and-burn clearing of forests

for agriculture, tropical forests may be completely eliminated within 25 years.

Plant diversity is a nonrenewable resource


• We have derived many medical compounds from the unique secondary compounds of plants.

• More than 25% of prescription drugs are extracted from plants, and many more medicinal compounds were first discovered in plants and then synthesized artificially.


Agenda 2/10• Go over practice quiz• Finish Fungi – slides and Animation 6-3-4 Characteristics of Fungi

only– Note to me- don’t spend time on life cycles of different groups

• • I will check your Ch. 31 notes while there• I can also sign rec forms today and next Wed. – Juniors should

consider Biotech, Anatomy, Physics/AP Physics, AP Environmental, AP Chem etc.

Homework-32 organizer and & 33 flashcards by next Mon.34 flashcards by next Wed.Test next Friday!!!!

• Decomposers- recycle dead material, can even breakdown cellulose and lignin

• Most plants depend on mutualistic fungi that help their roots absorb minerals and water from the soil.

• They help us make:– food, antibiotics and other drugs, bread rise, and

help to ferment beer and wine.

Why are fungi important?


Let’s look at that agar again!

Fungi characteristics

• Multicellular eukaryotes• More closely related to animals than plants• Fungi are heterotrophs that acquire their

nutrients by absorption.– They absorb small organic molecules from the

surrounding medium.– Exoenzymes, powerful hydrolytic enzymes

secreted by the fungus, digest food outside its body to simpler compounds that the fungus can absorb and use.

Different modes of nutrition

• Saprobes (decomposers) - absorb nutrients from nonliving organisms.

• Parasitic fungi absorb nutrients from the cells of living hosts – can be pathogenic

• Symbionts/Mutalists - – Mutualistic fungi also absorb nutrients from a

host organism, but they reciprocate with functions that benefit their partner in some way.


• The vegetative bodies of most fungi are constructed of tiny filaments called hyphae that form an interwoven mat called a mycelium.

Extensive surface area and rapid growth adapt fungi for absorptive nutrition


Fig. 31.1

• Fungal mycelia can be huge, but they usually escape notice because they are subterranean.– One giant individual of Armillaria ostoyae in Oregon is

3.4 miles in diameter and covers 2,200 acres of forest, – It is at least 2,400 years old, and weighs hundreds of

tons.

• Fungal hyphae have cell walls.– These are built mainly of chitin, a strong but flexible

nitrogen-containing polysaccharide, identical to that found in arthropods.


• Most fungi are multicellular with hyphae divided into cells by cross walls, or septa.– These generally have pores large enough for

ribosomes, mitochondria, and even nuclei to flow from cell to cell.

• Fungi that lack septa, coenocytic fungi, consist of a continuous cytoplasmic mass with hundreds or thousands of nuclei.

• This results from repeated nuclear division without cytoplasmic division.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin CummingsFig. 30.2a & b

• Parasitic fungi usually have some hyphae modified as haustoria, nutrient-absorbing hyphal tips that penetrate the tissues of their host.

• Some fungi even have hyphae adapted for preying on animals.


Fig. 30.2c & d

• The filamentous structure of the mycelium provides an extensive surface area that suits the absorptive nutrition of fungi.

• The fungal mycelium grows rapidly, adding as much as a kilometer of hyphae each day.

• The fungus concentrates its energy and resources on adding hyphal length and absorptive surface area.– While fungal mycelia are nonmotile, by swiftly

extending the tips of its hyphae it can extend into new territory.


• Fungi reproduce by releasing spores that are produced either sexually or asexually.– The output of spores from one reproductive

structure is enormous, with the number reaching into the trillions.

• Dispersed widely by wind or water, spores germinate to produce mycelia if they land in a moist place where there is food.

Fungi disperse and reproduce by releasing spores that are

produced sexually or asexually


• Many fungi form heterkaryotic mycelia after 2 hyphae fuse – nuclei can exchange chromosomes, compensate for mutations, etc.

• In many fungi with sexual life cycles, karyogamy, fusion of haploid nuclei contributed by two parents, occurs well after plasmogamy, cytoplasmic fusion by the two parents.– The delay may be hours, days, or even years.


Fig. 31.3

• More than 100,000 species of fungi are known and mycologists estimate that there are actually about 1.5 million speciesworldwide.

• Molecular analyses supports the division of the fungi into four phyla.

Diversity of Fungi


Fig. 31.4

• The four fungal phyla can be distinguished by their reproductive features.


• Mainly aquatic.

• Some are saprobes, some parasites

• Recent molecular evidence supports the hypothesis that chytrids are the most primitive fungi.

• most form coenocytic hyphae

• Motile flagellated spores

Phylum Chytridiomycota: Chytrids may provide clues about fungal origins


UNIQUE

• terrestrial, living in soil or on decaying plant and animal material.

• One zygomycete group form mycorrhizae, mutualistic associations with the roots of plants.

• Zygomycete hyphae are coenocytic, with septa found only in reproductive structures.

Phylum Zygomycota: Zygote fungi form resistant structures during

sexual reproduction


• The zygomycete Rhizopus (black bread mold) can reproduce either asexually or sexually.


Fig. 31.7

UNIQUE

• The zygosporangia are resistant to freezing and drying.

• When conditions improve, the zygosporangia release haploid spores that colonize new substrates.– Some zygomycetes,

such as Pilobolus, can actually aim their spores.


Fig. 31.8

• Mycologists have described over 60,000 species of ascomycetes, or sac fungi.

• They range in sizeand complexityfrom unicellularyeasts to elaboratecup fungi andmorels.

• Can be pathogens,decomposers, ormutualists(lichens ormychorrizae)

Phylum Ascomycota: Sac fungi produce sexual spores in saclike asci


Fig. 31.9

• The defining feature of the Ascomycota is the production of sexual spores in saclike asci.– In many species, the spore-forming asci are collected

into macroscopic fruiting bodies, the ascocarp.• Examples of ascocarps include the edible parts of truffles and

morels.

• Ascomycetes reproduce asexually by producing enormous numbers of asexual spores, which are usually dispersed by the wind.– These naked spores, or conidia, develop in long

chains or clusters at the tips of specialized hyphae called conidiophores.


Remember Sordaria from Meiosis Lab

• Ascomycetes are characterized by an extensive heterokaryotic stage during the formation of ascocarps.


UNIQUE

(1) The sexual phase of the ascomycete lifestyle begins when haploid mycelia of opposite mating types become intertwined and form an antheridium and ascogonium.

(2) Plasmogamy occurs via a cytoplasmic bridge and haploid nuclei migrate from the antheridium to the ascogonium, creating a heterokaryon.

(3) The ascogonium produces dikaryotic hyphae that develop into an ascocarp.

(4) The tips of the ascocarp hyphae are partitioned into asci.


(5) Karyogamy occurs within these asci and the diploid nuclei divide by meiosis, (6) yielding four haploid nuclei.

(7) Each haploid nuclei divides once by mitosis to produce eight nuclei, often in a row, and cell walls develop around each nucleus to form ascospores.

(8) When mature, all the ascospores in an ascus are dispersed at once, often leading to a chain reaction of release, from other asci.

(9) Germinating ascospores give rise to new haploid mycelia.

(10) Asexual reproduction occurs via conidia.


• Approximately 25,000 fungi, including mushrooms, shelf fungi, puffballs, and rusts, are classified in the phylum Basidiomycota.

Phylum Basidiomycota: Club fungi

have long-lived dikaryotic mycelia


Fig. 31.11

• The name of the phylum is derived from the basidium, a transient diploid stage.– The clublike shape of the basidium is

responsible for the common name club fungus.

• Basidiomycetes are important decomposers of wood and other plant materials.– Of all fungi, these are the best at decomposing

the complex polymer lignin, abundant in wood.

• Two groups of basidiomycetes, the rusts and smuts, include particularly destructive plant parasites.


(1) Two haploid mycelia of opposite mating type undergo plasmogamy, (2) creating a dikaryotic mycelium that ultimately crowds out the haploid parents.

(3) Environmental cues, such as rain or temperature change, induce the dikaryotic mycelium to form compact masses that develop into basidiocarps.– Cytoplasmic streaming from the mycelium swells the

hyphae, rapidly expanding them into an elaborate fruiting body, the basidiocarp (mushrooms in many species).

– The dikaryotic mycelia are long-lived, generally producing a new crop of basidiocarp each year.


(4) The surface of the basidiocarp’s gills are lined with terminal dikaryotic cells called basidia.

(5) Karyogamy produces diploid nuclei which then undergo meiosis, (6) each yielding four haploid nuclei.– Each basidium grows four appendages, and one haploid

nucleus enters each and develops into a basidiospore.

(7) When mature, the basidiospores are propelled slightly by electrostatic forces into the spaces between the gills and then dispersed by the wind.

(8) The basidiospores germinate in a suitable habitat and grow into a short-lived haploid mycelia.


• Asexual reproduction in basidiomycetes is much less common than in ascomycetes.

• A billion sexually-produced basidiospores may be produced by a single, store-bought mushroom.– The cap of the mushrooms support a huge

surface area of basidia on gills.– These spores drop beneath the cap and are

blown away.


• By concentration growth in the hyphae of mushrooms, a basidiomycete mycelium can erect basidiocarps in just a few hours.– A ring of mushrooms may appear overnight.– At the center of the ring are areas where the

mycelium has already consumed all the available nutrients.

– As the mycelium radiates out, it decomposes the organic matter in the soil and mushrooms from just behind this advancing edge.


Fig. 31.13

• Four fungal forms: molds, yeasts, lichens, and mycorrhizae, have evolved morphological and ecological adaptations for specialized ways of life.– These have occurred independently among the

zygote fungi, sac fungi, and club fungi.

Molds, yeasts, lichens, and mycorrhizae are specialized lifestyles that evolved

independently in diverse fungal taxa


• A mold is a rapidly growing, asexually reproducing fungus.– The mycelia of these fungi grow as saprobes

or parasites on a variety of substrates.– Early in life, a mold, a term that applies

properly only to the asexual stage, produces asexual spores.

– Later, the same fungus may reproduce sexually, producing zygosporangia, ascocarps, or basidiocarps.


Fig. 31.14

• Yeasts are unicellular fungi that inhabit liquid or moist habitats, including plant sap and animal tissues.– Yeasts reproduce asexually by simple cell

division or budding off a parent cell.– Some yeast reproduce sexually, forming asci

(Ascomycota) or basidia (Basidiomycota), but others have no known sexual stage (imperfect fungi).


Fig. 31.15

Yeast from a dog ear infection

• While often mistaken for mosses or other simple plants when viewed at a distance, lichens are actually a symbiotic association of millions of photosynthetic microorganisms held in a mesh of fungal hyphae.


Fig. 31.16

• The fungal component is commonly an ascomycete, but several basidiomycete lichens are known.

• The photosynthetic partners are usually unicellular or filamentous green algae or cyanobacteria.

• The merger of fungus and algae is so complete that they are actually given genus and species names, as though they were single organisms.– Over 25,000 species have been described.


• The fungal hyphae provides most of the lichen’s mass and gives it its overall shape and structure.

• The algal component usually occupies an inner layer below the lichen surface.


Fig. 31.17

• In most cases, each partner provides things the other could not obtain on its own.– For example, the alga provides the fungus with

food by “leaking” carbohydrate from their cells.– The cyanobacteria provide organic nitrogen

through nitrogen fixation.– The fungus provides a suitable physical

environment for growth, retaining water and minerals, allowing for gas exchange, protecting the algae from intense sunlight with pigments, and deterring consumers with toxic compounds.• The fungi also secrete acids, which aid in the uptake

of minerals.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• Lichens are important pioneers on newly cleared rock and soil surfaces, such as burned forests and volcanic flows.– The lichen acids penetrate the outer crystals of

rocks and help break down the rock.– This allows soil-trapping lichens to establish

and starts the process of succession.– Nitrogen-fixing lichens also add organic

nitrogen to some ecosystems.


• Mycorrhizae are mutualistic associations of plant roots and fungi.– The anatomy of this symbiosis depends on the

type of fungus.

• The extensions of the fungal mycelium from the mycorrhizae greatly increases the absorptive surface of the plant roots.

• The fungus provides minerals from the soil for the plant, and the plant provides organic nutrients.


Fig. 31.18

• Mycorrhizae are enormously important in natural ecosystems and in agriculture.– Almost all vascular plants have mycorrhizae

and the Basidiomycota, Ascomycota, and Zygomycota all have members that form mycorrhizae.

– The fungi in these permanent associations periodically form fruiting bodies for sexual reproduction.

– Plant growth withoutmycorrhizae is often stunted.


• About 30% of the 100,000 known species of fungi are parasites, mostly on or in plants.– Invasive ascomycetes have had drastic effects

on forest trees, such as American elms and American chestnut, in the northeastern United States.

– Other fungi, such as rusts and ergots, infect grain crops, causing tremendous economic losses each year.

Some fungi are pathogens


Fig. 31.20

• Animals are much less susceptible to parasitic fungi than are plants.– Only about 50 fungal species are known to parasitize

humans and other animals, but their damage can be disproportionate to their taxonomic diversity.

• The general term for a fungal infection is mycosis.– Infections of ascomycetes produce the disease

ringworm, known as athlete's foot when they grow on the feet.

– Inhaled infections of other species can cause tuberculosis-like symptoms.

– Candida albicans is a normal inhabitant of the human body, but it can become an opportunistic pathogen (vaginal yeast infection).


• Yeast are even more important in food production.– Yeasts are used in baking, brewing, and winemaking.

• Contributing to medicine, some fungi produce antibiotics used to treat bacterial diseases.– In fact, the first antibiotic discovered was penicillin,

made by the common mold Penicillium.


Fig. 31.21

• The fossil record indicates that terrestrial communities have always been dependent on fungi as decomposers and symbionts.

• The oldest undisputed fossil fungi date back 460 million years, about the time plants began to colonize land.

• Fossils of the first vascular plants from the late Silurian period have petrified mycorrhizae.

• Plants probably moved onto land in the company of fungi.

Fungi colonized land with plants


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