PHOTOSYNTHESIS

Photosynthesis packages the energy of light into organic molecules using CO2 and water as the raw materials to manufacture the organic products.

Photosynthetic organisms are autotrophs. To understand photosynthesis, you must know a little about the

properties of light, which drives the process. In 1905, Einstein proposed that light consists of packets of energy

called photons, which are the smallest divisible units of light. The energy of a photon is inversely proportional to the wavelength of

the light: the longer the wavelength, the less energy per photon. We perceive the different wavelengths as different colors. All of the colors of light come together and form white light, or visible

light. Photosynthetic organisms harvest sunlight and use it to drive

photosynthesis, the process that feeds most of the earth. The energy of a photon is inversely proportional to the wavelength of

the light: the longer the wavelength, the less energy per photon. We perceive the different wavelengths as different colors. All of the colors of light come together and form white light, or visible

light. Photosynthetic organisms harvest sunlight and use it to drive

photosynthesis, the process that feeds most of the earth. Light is absorbed by complex, organic molecules called pigments,

which appear colored because they also reflect light. Chlorophyll are the primary green pigments of photosynthesis. Photosynthesis requires both photochemical and biochemical reactions

to produce sugars. In 1905, F.F. Blackman provided the first evidence that photosynthesis

is a two-stage process. The photochemical reactions became known as the light reactions

while the biochemical reactions became known as the Calvin cycle. Chloroplasts are the site of photosynthesis in plants. Each chloroplast is surrounded by two membranes that enclose a

gelatinous matrix called the stroma. Suspended in the stroma are neatly folded sacs of membranes called

thylakoids. Thylakoids are stacked into grana. Thylakoids contain the chlorophylls and accessory pigments and are

where light is absorbed during photosynthesis.

LIGHT REACTIONS The light reactions of photosynthesis produce ATP. This light-dependent production of ATP in a chloroplast is called

photophosphorylation. Light provides the energy for addition of a phosphate (Pi) to ADP,

making ATP: ADP + Pi + light → ATP + water The light reactions of photosynthesis also produce NADPH. NADPH (nicotinamide adenine dinucleotide phosphate) is also an

energy carrying molecule like ATP.THE BIOCHEMICAL REACTIONS

The biochemical reactions convert CO2 to carbohydrates. The biochemical reactions associated with photosynthesis convert

atmospheric CO2 to carbohydrates, primarily sucrose and starch. Sucrose, a simple sugar, and starch, a complex carbohydrate. Conversion of CO2 to sugars is also called carbon fixation. Carbon fixation- the carbon is fixed in organic form (organic molecules

have carbon to carbon bonds)Carbon Cycle (Nobel Prize Winner, Melvin Calvin)

The cycle of biochemical reactions that fix and assemble CO2 is called the Calvin cycle.

The Calvin cycle can be followed through the following details: CO2 bonds to RuBP to produce an organic compound– PGA. The enzyme that catalyzes the carbon fixation reaction is rubisco

(RuBP carboxylase/oxygenase). Rubisco is a large, complex enzyme that has been called the most

important and most abundant protein on earth.Rubisco

The assembly of rubisco inside a chloroplast is controlled by light. It makes up to 50% of the protein in leaves and is made at a rate of 4 x

1010 grams per year. In the next steps, which are powered by ATP and NADPH, each

molecule of 3-PGA is converted to PGAL (glyceraldehyde-3-phosphate) PGAL is a three-carbon sugar. A summary equation is represented this way:

3 CO2 + 6H2O → C3H6O3P +3O2 + 3H2OPGAL

PGAL is a triose-P (triose-phosphates), having three-carbon atoms with a phosphate group attached to it.

Some of the triose-P is used to re-form RuBP and keep the cycle running in the light.

Triose-P is also used to make sucrose, ensuring some consistency of sucrose supply in a plant.

Sucrose provides the carbon and energy for biosynthesis of other organic compounds in all parts of a plant.

What is Ecology?→ Ecology is the study of interactions between an organism and its environment.

→ E.g. raccoons and persimmonsWhat is Evolution?→ the natural or artificially induced process by which new and different organisms develop as a result of changes in genetic materialHow are Ecology and Evolution intimately linked in the lives of organisms?→ In a way that individuals that survive in their environment reproduce and contribute to the evolution of their species

Raccoon and Persimmon - Adaptation

Plants are indicators of the environment.An organism that can survive, grow, and reproduce is said to be adapted to its particular environment.An adaptation is a heritable characteristic that allows an organism to live in a particular environment. The fleshy fruit of the persimmon is an adaptation that attracts animals that may disperse its seeds.Because plants have adaptations that allow them to live in their particular environment, you may be able to determine a plant’s environment just by looking at its characteristics.

Lesser burdock plant, rose hip, milkweed, berry, willow, coconut palm

Plants are indicators of the environment.• For instance, spines not only protect a cactus from herbivores but keep

it from losing too much precious water in the dry, desert heat.• Thus finding a plant with spines may indicate that the environment in

which this plant normally lives receives little precipitation.• The form and function of plants often indicate physical and biotic

factors with which they have evolved.

Christmas cactus, organ pipe cactus, Saguaro cactus, barrel cactus, prickly pear cactus, jumping cholla cactus

Dispersal of fruits and seeds reduces seed predation and competition.• Competition is an ecological interaction between two organisms to

acquire a resource that both need and that is in limited supply– such as H2O, sunlight, or minerals.

• If all seeds drop directly below the parent plant, a seed predator– an herbivore that eats seeds– may be able to find and eat most of them.

• When a seed germinates next to a mature plant, the young seedling may not get enough resources it needs for continued growth, due to competition with the mature plant.

• Dispersal occurs either by physical or biological carriers.• Wind and water are the physical carriers, whereas animals are the

main biological carriers.

Trillium, a spring ephemeral, blooming early in spring, Massachusetts.

The germination of a seed and growth of a plant depend on favorable environmental conditions.• Within a seed, the embryo is dormant, meaning that it is alive but not

actively growing.• After a seed has been dispersed, it may begin to grow if environmental

conditions are favorable.• The most common external factors that break seed dormancy are

water, temperature, and light.• The seeds of woody plants in temperate climates often require a wet

period that is followed by several weeks of cold before they germinate (stratification).

• Many seeds germinate only after the seed coat is scratched or cracked or soaked in conc. acid (scarification).

Fruits such as apples that were once only available during specific harvest seasons, are now available to consumers year round in many parts of the world.

Many seeds lie dormant in a seed bank in the soil.• Everywhere that seed plants grow, the soil contains viable,

ungerminated seeds in natural storage– that is, in a seed bank. How long can seeds remain viable?→Longevity varies among diff. kinds of plants and with environmental conditions.→The record for longevity, however, belongs to the arctic tundra lupine seeds that are estimated to be about 10,000 years old.

Arctic tundra

Plants must deal with the environment both above- and belowground.

• Plants must live in two worlds at the same time.1. The relatively cool and moist underworld of the soil2. The lighted, windy world aboveground that can fluctuate from below

freezing to extremely hot temperatures• Because of the environment in which they grow, what characteristics

might a stem require that a root system would not?

• What characteristics might a stem require that a root system would not?

• Plants maintain a balance between their root system and shoot system.

• If either the shoot or root systems become too large the plant may die.• There is an ecological trade-off, that is a negative aspect of the

characteristic for every positive aspect.• E.g. the greater size of leaves, which gives the plant an advantage for

photosynthesis, allows a greater loss of water through transpiration.

A simple leaf, such as this example from a maple tree, may have an ecological trade-off because of its large leaves.

• Transpiration is water loss from a plant through its stem and, mostly through its leaves.

• Almost all transpiration occurs through small pores called stomata (singular, stoma) in the surface of leaves.

• When stomata are open, carbon dioxide can enter the leaf and be used as a raw material to produce sugar.

• However, as long as the stomata are open, water also is lost.• Some plants possess hairs on their leaves that help reduce

transpiration.

Tomatillo (plant with a hairy leaf)

• All individuals are part of a population, which is a part of a community of organisms.

• Population is a group of individuals of the same species sharing the same territory, or range, at the same time and interbreeding with each other.

• Plants are the producers of a community.• Community consists of populations of different species living and

interacting in the same location.• In a community, herbivores (plant eaters) depend directly on plants for

their energy.

herbivores: koala bear and white-tailed deer

• Other animals, carnivores (meat eaters), may eat herbivores to obtain energy.

• Food chain connects the producers of the community with the consumers of the community.

• Food web is the interlocking food chains within an ecological community.

• Another group of organisms depends on dead organisms or their parts to make their living in the community (decomposers).

• Organisms in a community are linked by their use of energy and nutrients and are grouped into trophic/nutritional levels.

• A trophic level is a stage in a food chain that reflects the number of times energy has been transferred through feeding.

Food web

NOTES ephemeral- short-lived dormant- not actively growingstratification- formation of layers (soil)seed coat- prtotects the seedscarification-seed bank- soilarctic tundra lupine

Plant Physiology: Environmental FactorsTemperature

extremes of this range may be considered killing frosts at about 32ºF (0ºC) and death by heat and desiccation at about 105ºF (40ºC).

Air Temperature optimum air temperature range

o 12 and 24ºC

o 18ºC- cool season plants/ warm season plantsSoil Temperature

Soil temperature has direct dramatic effects on microbial growth and development, organic matter decay, seed germination, root development, and water and nutrient absorption by roots.

Effects• Chilling Injury - 10ºC ; more sensitive to cold temperatures shortly

before flowering• Heat Stress - 45-55ºC ; • Vernalization - The exposure of certain plants to low temperatures

induces or accelerates flowering (bolting). “seeds can be vernalized”

Light• affects the morphological development (size/proportion of root and

shoots) of the plant• imparting to the plant some type of ecological or physiological

advantageLight Quality• Sunlight is often referred to as white light and is composed of all colors

of light• red (600 to 660 nm) and far red (700 to 740 nm) wavelengths of the

electromagnetic spectrum appear to be important in the light-regulated growth of plants photosynthesis are generally broader (400 to 700 nm)

Light Intensity• “quantity of light” • affected by the intensity of the incident (incoming) light and the

length of the day• light saturation point of the plant determines the relative light

requirement of plant

Light Regulated Plant Development – Photomorphogenesisinternode elongationchlorophyll developmentfloweringlateral bud outgrowthroot and shoot growth

Water Waterlogging

all pores in the soil or soilless mixture are filled with water so the oxygen supply is almost completely deprivedCauses death of root hairs, reduces absorption of nutrients and water, increases formation of compounds toxic to plant growth, and finally retards growth of the plant.

Water Balance

available moisture in the soil (or soil mix), or the transpiration of water through the stomata exceeds the plant’s capacity to compensate for the internal lossadjust to short-term water stress by closing stomates and thereby reducing water loss through the leaves

WindAir movement and distribution within the greenhouse can be enhanced with horizontal airflow fans.

Growing Mediamoisture holding capacity

nutrient exchange capacitygas exchange of oxygen and carbon dioxidefoundation for the plant roots to support the plant

XEROPHYTEPlants that live in conditions where water is scarce (for example in the desert)

MESOPHYTELand plants living in environment with moderate amount of moisture.

HYDROPHYTEA plant adapted to grow in water

Plant Fertility Plant macronutrients

nitrogen (N)phosphorus (P) potassium (K)calcium (Ca)magnesium (Mg) sulfur (S)

Plant micronutrientsiron (Fe) cobalt (Co)copper (Cu) molybdenum (Mo)manganese (Mn) boron (B)zinc (Zn) chlorine (Cl)

Relationship with other organismCompetition - struggle for resources: the struggle between organisms of the same or different species

for limited resources such as food or light

Mutualism - advantageous relationship between species: a relationship between two organisms of

different species that benefits both and harms neither.

For example, lichens are a fungus and an alga living in mutualism: The fungus provides a protective structure, and the alga produces a carbohydrate as food for the fungus.

Predation - preying of one species on another: the relationship between two groups of animals in which

one species hunts, kills, and eats the other

Parasitism - parasitic behavior: symbiosis in which one organism lives as a parasite in or on another

organism

Commensalism - symbiosis between unrelated organisms: the relationship between organisms of two

different species in which one derives food or other benefits from the association while the other remains unharmed and unaffected

COMMON NAME VS. SCIENTIFIC NAME• Common Name - a name in general use within a community; it

is often contrasted with the scientific name for the same organism.

• Scientific name - The recognized Latin name given to an organism, consisting of a genus and species, according to a taxonomy; also called the binomial name.

Disadvantages of Common Name to OrganismDisadvantages

Common names are confusing.Common names do not provide the scientific basis for classifying any certain things.Problem occurs when a species has more than one common name. More than one name used in one place.Two or more names in different languages. 

AdvantagesCommon names are easy to remember.

Advantages of Scientific NamesAdvantage1) only one name per species 2) recognized and documented worldwide 3) same in any language

Disadvantages1.) More difficult to remember and pronounce the Latin format. 2.) name unfamiliar, not as commonly known.

Taxonomy - The science of naming, identifying and classifying organism.

Brief History of Taxonomy and DevelopmentAristotle• First person who attempted to classify organisms.• Grouped living things according to two- plants and animals.

Philippus Theophrastus• First attempted to organize and classify plants in the 4th century B.C.• Grouped plants according to stem structure.

John Ray• Identified and classified more than 18,000 different types of plants and

also classified the members of several different animal groups.• First to use the term SPECIES for each kind of organism.

However, Aristotle’s classification posed a lot of problem.For example, where do frogs and salamanders fit? They spend their life both in water and on land.

Thus, THERE IS A NEED FOR A SYSTEMATIC CLASSIFICATION.

During Middle Ages, ordinary people used common names in identifying organisms.

Common names describes the structure or physical attributes of an organism,To help biologists understand one another, the use of LATIN in naming organisms was introduced.

Why LATIN?Modern Taxonomy Karl von Linne (Carolus Linnaeus)• A physician and botanist from sweden who began the modern system

of classification in 1758.• Founder of modern taxonomy.• Introduced the binomial system of nomenclature (two-name).

Binomial System of NomenclatureFormal system of naming organisms consists of two Latinized names, the genus and the species.

The binomial aspect of this system means that each organism is given two names, a ‘generic name,’ which is called the genus(pl. genera) and a ‘specific name,’ the species.

Genus‘Genus’ is the taxonomic classification lower than ‘family’ and higher than ‘species’.

In other words, genus is a more general taxonomic category than is species. 

SpeciesA species name, also called specific epithet, is the second part of a scientific name.

Refers to one species within a genus.

How to Write scientific name?There are precise convention to follow when writing a scientific name. 

Genus Name1. The genus name is written first.2.  The genus name is always underlined or italicized. 3. The first letter of the genus name is always capitalized.Example:

A strophytum  or Astrophytum

Scientific Name1. The specific epithet is written second.2. The specific epithet is always underlined or italicized.3. The first letter of the specific epithet name is never capitalized.Example: m yriostigma  or myriostigma

The scientific name of this plant would appear as follows:

A strophytum   m yriostigma  or Astrophytum myriostigma

• Every organism that has ever existed can be fitted into the scheme in a logical and orderly manner, for the system is capable of indefinite expansion.

• The various hierarchical levels in the system provide a conceptual framework for understanding the relationships among different organisms or groups of organisms.

• The general system provides a framework for biological classification.a. Kingdomb. Phylumc. Classd. Ordere. Familyf. Genusg. Species

“King Phillip Came Over for Green Spaghetti”

Levels of Classification

• Linnaeus grouped organisms into taxonomic categories.• They are the domain, kingdom, phylum or division, class order, family,

genus, and species.• Classification goes in a hierarchical order. This starts with domain.

There are three domains of life:o Bacteriao Eukaryotao Archaea

• Domain - Highest taxonomic rank of organisms, higher than a kingdom.  Domain Bacteria

Prokaryotic, unicellular, auto or heterotrophicMost have cell wall made up of peptidoglycan and have ribosomesAutotrophs can get energy from

sun (photosynthetic) or from inorganic substances

Domain ArchaeaProkaryotic, unicellular, auto or heterotrophicusually live in harsh environmentsoxygen free (anaerobic), very hot or acidic, or very salty environmentschemically different from other bact.cell walls do not contain peptidoglycan

Domain EubacteriaProkaryotic, unicellular, autoheterotrophic“true” bacteria- can be found just about everywhereCan be classified by shape, chemical composition, motility and metabolism

Robert WhittakerIn 1969, he proposed a five kingdom system of classification for living organism.

The kingdoms are distinguished partly by how they obtain food. There are five basic kingdoms:

Kingdom Plantae• Eukaryotic, multicellular,

autotrophic• Take up water and nutrients in

roots; make food in leaves (photosynthesis)

• sexual reproduction (alternation of generations)

Kingdom Animalia• Eukaryotic, multicellular,

heterotroph• Specialized cells from into tissues and organs

• Most are able to move (some are sessile)• Invertebrates (no spinal cord) or Vertebrate (spinal cord)

Kingdom Monera• Prokaryotes• Heterotrophic and autotrophic• Anaerobic and aerobic• aquatic, terrestrial and in the air• mostly asexual• mostly non motile (1 form does move)

Kingdom Protista• Eukaryotes• Heterotrophic and Autotrophic• Unicellular• Mostly aquatic• Mostly asexual• Motile and nonmotile

Kingdom Fungi• Eukaryote• Heterotrophic• Unicellular and Multicellular• Mostly terrestrial• asexual and sexual• nonmotile

Importance of 5 Kingdoms of LifeWhy do we need to study kingdoms of life?• It makes the study of such a wide variety of organisms easy.• It projects before us a good picture of all life forms at a glance.• It helps us understand the interrelationship among different groups of

organisms.• It serves as a base for the development of other biological sciences

such as biogeography etc.• Various fields of applied biology such as agriculture, public health and

environmental biology depends on classification of pests, disease vectors, pathogens and components of an ecosystem.

Five kingdom system of Robert Whittaker is based:• complex nature of cell structure• body organization• cell• mode of nutrition

Mode of NutritionNutrition can be defined as the process by which an organism obtains food which is used to provide energy and materials for its life sustaining activities.

Note:• Prokaryotes - simple organism without

nucleus: an organism whose DNA is not contained within a nucleus, e.g. a bacterium)

• Eukaryotes - organism with visible nuclei: any organism with one or more cells that have visible nuclei and organelles.

o The group contains all living and fossil cellular organisms except bacteria and cyanobacteria.

Note:• Heterotrophic getting nutrients through food digestion: obtaining nourishment by digesting plant or animal matter, as animals do, as opposed to photosynthesizing food, as plants do • Autotrophicable to manufacture nutrients: describes organisms, especially green plants, that are capable of making nutrients from inorganic materials

The chemical substances that provide nourishment to living organisms are called nutrients.

Depending on the mode of nutrition the organisms are classified as autotrophs and heterotrophs.

Complex nature of Cell StructureMade up of different structure performing different function.

CellStructural unit of life.Has two types: prokaryotic and eukaryotic.

Prokaryotic cellIncludes archaea and bacteriaA singled cell organism that does not have nucleus.They are not complicated unlike eukaryotic.

Eukaryotic cellA more complex cell with nucleus and many organelles.Includes plants, animals, fungi, and protist.

Body OrganizationMade up of different cells forming tissues, and different tissues forms organs and various organs are arranged into an organ system to perform differen functions.ANGIOSPERM“the flowering plants”(Angiospermae or Magnoliophyta)

• ANGIOSPERMS are seed-producing plants like the GYMNOSPERMS.• Some of their characteristics include:

- flowers- endosperm within the seeds - production of fruits that contain the seeds.

• The ancestors of flowering plants diverged from gymnosperms around 245–202 million years ago.

ENDOSPERM

Angiosperm characteristics:1. Flowers - reproductive organs

of flowering plants2. Stamens with two pairs of

pollen sacs

3. Reduced male parts- the male gametophyte in angiosperms is significantly reduced in size compared to those of gymnosperm seed plants.

4. Closed carpel enclosing the ovules

5. Reduced female gametophyte, seven cells with eight nuclei2 pairs of pollen sacs

6. Endosperm - begins after fertilization and before the first division of the zygote; a highly nutritive tissue that can provide food.

These distinguishing characteristics have made the angiosperms the most diverse and numerous land plants.

The Flower and Its PollinationIn angiosperms, meiosis in the sporophyte generation produces two kinds of spores.

1. microspores– develop in the microsporangium – germinate and develop into the male gametophyte generation

2. megaspores– develop in the megasporangium– develop into the female gametophyte generation.–

– Both types of sporangia are formed in flowers.– In most angiosperms, the flowers are perfect: each has both

microsporangia and megasporangia.– Some angiosperms are imperfect, having either microsporangia or

megasporangia but not both.

ASEXUAL PROPAGATION• multiplication without passage through the seed cycle• best way to maintain some species• to multiply or clone plants rapidly

 Major methods of asexual propagation:1. Cuttings - vegetative plant part which is severed from the

parent plant in order to regenerate itself, forming a whole new plant.

- involve rooting a severed piece of the parent plant- many types of plants, both woody and

herbaceous, are frequently propagated by cuttings3. Air or ground layering - involves rooting a part of the parent and

then severing it4. Budding and grafting - joining plant parts so they will grow as one

plant.5. Stolons or runners6. Storage organs

STEPS IN AIR LAYERING

Heated propagator - horticultural device to maintain a warm and damp environment for seeds and cuttings to grow in.

GROUND LAYERING

Kingdom PlantaeBryophytesNon-seeded vascular plantsGymnosperms Angiosperms

Land plants evolved from green algae

Researchers have identified green algae called charophyceans as the closest relatives of land plants

Defining the Plant Kingdom

Systematists are currently debating the boundaries of the plant kingdom

Derived Traits of Plants

Five key traits appear in nearly all land plants but are absent in the charophyceans

• Apical meristems

• Alternation of generations

• Walled spores produced in sporangia

• Multicellular gametangia

• Multicellular dependent embryos

Derived trait - a trait that is present in an organism, but was absent in the last common ancestor of the group being considered.

Apical meristems and al ternation of generations

Extant - still in existence; not destroyed, lost, or extinct

Bryophyta Bryophytes are represented today by three phyla of small

herbaceous (nonwoody) plants• Liverworts, phylum Hepatophyta• Hornworts, phylum Anthocerophyta• Mosses, phylum Bryophyta

In all three bryophyte phyla• Gametophytes are larger and longer-living than sporophytes

Characteristics Includes liverworts, hornworts, and mosses Lack vascular tissue (xylem & phloem) to carry water and food Go through Alternation of generations (sporophyte & gametophyte

stage) Gametophyte is dominant stage (haploid) Reproduce by spores

Bryophyte diversity

Liverworts (Phylum Hepatophyta) Named for the liver-shaped gametophytes of its members "thalloid liverworts" have flattened gametophytes "leafy liverworts" have stem-like gametophytes with many leaf-

like appendages. There are many more species of leafy liverworts than thalloid

liverworts.

Hornworts (Phylum Anthocerophyta)

The common name refers to the long, tapered shape of the sporophyte.

Mosses (Phylum Bryophyta) Moss gametophytes, which range in height from less than 1mm up to

2mm, are less than 15 cm in most species. The blades of their "leaves" are usually only one cell thick. Sporophytes are typically elongated and visible to the naked eye,

with heights ranging up to about 20 cm.

Ecological and Economic Importance of MossesSphagnum, or “peat moss”

• Forms extensive deposits of partially decayed organic material known as peat

• Plays an important role in the Earth’s carbon cycle

Non-seeded Vascular Plants Ferns and other seedless vascular plants formed the first forests Bryophytes and bryophyte-like plants

• Were the prevalent vegetation during the first 100 million years of plant evolution

Vascular plants• Began to evolve during the Carboniferous period

Evolution of Leaves Leaves

• Are organs that increase the surface area of vascular plants, thereby capturing more solar energy for photosynthesis

Leaves are categorized by two types• Microphylls, leaves with a single vein• Megaphylls, leaves with a highly branched vascular system

According to one model of evolution,Microphylls evolved first, as outgrowths of stems

Sporophylls

• Are modified leaves with sporangia Most seedless vascular plants

• Are homosporous, producing one type of spore that develops into a bisexual gametophyte

Classification of Seedless Vascular PlantsSeedless vascular plants form four divisionsincluding club mosses, spike mosses, quillworts, ferns, horsetails, whisk ferns and their relatives.

Divisions Psilophyta – Whisk ferns Lycophyta – Club mosses Sphenophyta – horsetails Pterophyta - ferns

Characteristics Have specialized transport or vascular tissues (xylem & phloem) to carry food

& water Have sporophyte & gametophyte stages (alternation of generations) SPOROPHYTE is dominant Reproduce by spores

Division PsilophytaWhisk Ferns

Have a photosynthetic, aerial forked stem Looks like a small, green twiggy bush Have TRUE stems, but NO leaves or roots Only two living genera Have rootlike stems structures called

Rhizomes to anchor (can’t absorb water) May asexually reproduce from rhizomes Sexually reproduce by spores made in

Sporangia (spore cases on the stems)Division LycophytaClub Moss

Commonly called ground pines Bushy, tree like branches above, but unbranched

at the base Have deep growing root like Rhizomes

(b) Megaphylls, which have branched vascular systems, may have evolved by the fusion of branched stems.

(a) Microphylls, such as those of lycophytes, may have originated as small stem outgrowths supported by single, unbranched strands of vascular tissue.

Vascular tissue

Live in moist woods and clearings Small leaves with single unbranched vein Sporophylls (spore cases) are found in the axils of leaves Form cone shaped structures called Strobili May be homosporous (make one type of spore) or

heterosporous (make 2 types of spores)

Club Moss Spores Genus Lycopodium is homosporous Contain chemicals that explode & burn quickly Yellowish powdery spores used in fireworks and explosives

Club Moss SporophyllsOther Uses for Club Moss

Sometimes boiled in water to produce a medicinal tea or an eye wash

Ground pines, green all winter, are used in Christmas decorations

Ancestors of modern club mosses helped form coal during the carboniferous period

Division SphenophytaHorsetails

Only one living (extant) species - Equisteum Also called scouring rushes Hollow, jointed Stems contain silica & were once used to

scrub pots Photosynthetic aerial stem Underground Rhizomes Reproduce by spores at the tips of branches In prehistoric times, grew as tall as trees Found in wetlands Stems with sunken stomata to save water Some spores have elaters, cells that act as moisture-

sensitive springs, assisting spore dispersal

Uses for Horsetails Used to fight plant fungi Used in some mouthwashes to cure mouth ulcers Used as diuretics to eliminate excess water (weight loss products) Toxic to animals (sheep, cattle, horses)

Division Pterophyta (Ferns) Largest group of extant (living) vascular plants Wide range of habitats (terrestrial, aquatic, arboreal tree ferns, epiphytic) Can asexually reproduce by Rhizomes (underground stems) Dominant Sporophyte stage has true roots, stems, and leaves Roots and stems underground Leaves called fronds found above ground and attached to a stem like petiole Newly forming fronds called fiddleheads must uncurl

Spore cases called sori are found on the underside of fronds Wind spreads spores that land on moist soil &

germinate into a prothallus The prothallus starts the Gametophyte stage Gametophyte is heart shaped and short lived Male antheridia & female archegonia grow on

gametophyte Sperm swims to egg to fertilize

Uses for Ferns Help prevent

erosion Fiddleheads are

eaten as food Ornamental plants

for yards and homes Helped form coal deposits millions of years ago

Concept 2: Gymnosperms bear “naked” seeds, typically on cones Among the gymnosperms are many well-known conifers

• Or cone-bearing trees, including pine, fir, and redwood

The gymnosperms include four plant phyla• Cycadophyta

• Gingkophyta• Gnetophyta• Coniferophyta

Gymnosperms appear early in the fossil record • And dominated the Mesozoic terrestrial ecosystems

Living seed plants• Can be divided into two groups: gymnosperms and

angiosperms

Characteristics of Angiosperms Phylum Anthophyta The key adaptations in the evolution of angiosperms

• Are flowers and fruits

The flower• Is an angiosperm structure specialized for sexual reproduction

Fruits• Typically consist of a mature ovary