1 Seed Plants Gymnosperms & Angiosperms. 2 Evolution Of Land Plants REMEMBER: Terrestrial plants...

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Seed PlantsSeed Plants

Gymnosperms & Gymnosperms & AngiospermsAngiosperms

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Evolution Of Land Evolution Of Land PlantsPlants

REMEMBER:REMEMBER:• Terrestrial plants evolved from Terrestrial plants evolved from

a green a green algal ancestoralgal ancestor• The earliest land plants were The earliest land plants were

nonvascular, sporenonvascular, spore producers producers (bryophytes)(bryophytes)

• FernsFerns were the were the 11stst vascular, vascular, sporespore producing plants producing plants

• Gymnosperms & angiospermsGymnosperms & angiosperms were the were the 11stst vascular vascular, , seedseed plantsplants

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• MulticellularMulticellular• AutotrophicAutotrophic• Alternation of Alternation of

GenerationsGenerations• Reproduce by Reproduce by

SeedsSeeds• Vascular tissueVascular tissue for for

transporttransport• HeterosporousHeterosporous – –

make female make female megasporesmegaspores & male & male microsporesmicrospores

Characteristics of Seed Characteristics of Seed PlantsPlants

Dandelion dispersing seeds

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Reasons for Success on Reasons for Success on LandLand

• Waxy cuticle• Stomata with guard cells to

open & close• Gametes protected in tissue

called Gametangia• Pollen tube to transfer sperm

to the egg instead of water• Seeds protect developing

embryo & contain food

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Seeds and FruitsSeeds and Fruits

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SeedsSeeds• Seeds contain a young,

developing plant embryo• Seeds are covered with a

protective seed coat (testa)

• Inside is stored food or endosperm that the young plant uses as it begins to sprout or germinate

• Seeds form from ripened ovules after fertilization

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Parts of a Seed EmbryoParts of a Seed Embryo

• Primary root or Radicle• One or two embryonic leaves

called Cotyledons• Plumule becomes the shoot • Stem like portion below

cotyledons called Hypocotyl• Stem like portion above

cotyledons called Epicotyl

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Parts of a SeedParts of a Seed

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Endosperm (3n)

Seed Coat

CotyledonPlumule

Epicotyl

Hypocotyl

Radicle

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Seed DispersalSeed Dispersal• Seeds must be

scattered (dispersed) away from the parent plant

• Testa (seed coats) may last thousands of years

• Seeds eaten by animals aren’t digested but pass out with wastes

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Seed DispersalSeed Dispersal

• Seeds may have adaptations such as stickers, hooks, or fuzz to adhere to animals

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Seed DispersalSeed Dispersal

•Both water and wind can scatter seeds

Wind Dispers

al

Water Dispersal

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Seed GerminationSeed Germination

• Early growth of plant embryo

• Begins when seed absorbs water & breaks seed coat (testa)

• Embryo uses stored food of cotyledons to begin growing

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FruitsFruits• Form when ovary with ovules

(eggs) ripens• May be dry and hardened

(nuts)• May be enlarged and fleshy

(berries, apples, tomatoes)• Used to help disperse seeds

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Types of FruitsTypes of Fruits

• Simple fruits – form from a single ovary (apple)

• Aggregate fruits – forms from several ovaries of the same flower (blackberry)

• Multiple fruit – forms from several ovaries of different flowers (inflorescence)

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Plants with Plants with Vascular TissueVascular Tissue

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gymnosperrms

angiosperms

Taxonomy of Vascular Taxonomy of Vascular Seed PlantsSeed Plants

• Phylum Gnetophyta: Ephedra, Gnetum

• Phylum Cycadophyta: Cycads• Phylum Ginkgophyta: Ginkgo• Phylum Coniferophyta:

Conifers• Phylum Anthophyta:

Flowering plants

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Sporophyte

microsporangium megasporangiumxmicrospores megasporesx

microgametophyte megagametophytex

antheridium archegonium lsperm eggmm

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Seed plants (Ch.30)

Tiny gametophytes protected in ovules and pollen grains

Advantages of seeds

Gymnosperms have “naked seeds”

Angiosperms have seeds in fruits

Monocots

Eudicots

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• Gymnosperm– Intro and evolution– Life cycle and

reproduction– Uses and significance

• Angiosperms: Flowering plants– Intro and evolution– Life cycle and

reproduction– Uses and significance– Monocots vs. dicots

12: Gymnosperms and 12: Gymnosperms and AngiospermsAngiosperms

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Kingdom Plantae• Evolutionary tree of plants• From primitive more advanced

traits

Bryophytes

Greenalgaancestor

_______ Gymnosperms __________

Vascular

________

Terrestrial

Flowers

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GYMNOSPERMS• Introduction – Gymnosperm means

“naked seed” (From the Greek: gymnos = naked; sperm = seed)

• More advanced than ferns – do not have spores, they have seeds.

• The seeds of the gymnosperms lack a protective enclosure (unlike flowering plants which have flowers and fruit).

• Examples of gymnosperms: • Conifers (pine trees), cycads,

ginkgo biloba

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Evolution of gymnosperms• Gymnosperms evolved from fern-like

ancestors• Advancements of gymnosperms over

ferns:• 1. Seed (plant embryo, food storage tissue,

and seed coat) • 2. Gymnosperms do not depend on water

for fertilization (have air-borne pollen)• 3. Have a more dominant sporophyte

generation• 4. Have a more efficient vascular system

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Gymnosperm life cycle

• Exhibits alternation of generations• Sporophyte generation (2n) is dominant• Gametophyte generation (1n) is contained in and

dependent on the sporophyte generation

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Gymnosperm lifecycle

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Sporophyte generation• Sporophyte produces two types of

spores (heterosporous)• Megasporangium – undergoes

meiosis to produce megaspores (female gametophyte)

• sporangium – undergoes meiosis to produce haploid microspores, germinate to produce male gametophyte (pollen)

• Many gymnosperms use wind for pollination and seed dispersal

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Wood produced by gymnosperms

• Gymnosperms have a very efficient and effective vascular system

• Usually woody plants• Xylem wood of a tree• Phloem bark of the tree• Wood is formed

from secondary growth

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Primary vs. secondary growth

• 1. Primary growth – occurs in apical meristems of shoots and roots

• Results in increase in length

• 2. Secondary growth – derived from secondary or lateral meristems

• Results in increase in girth (width)

• Common in trees (wood and bark)

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Secondary growth• The cambium forms secondary xylem

and secondary phloem• Wood – is secondary xylem; cells are

dead at maturity and only cell wall remains

• Bark – is secondary phloem (conducts food)

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Annual rings• Annual rings – xylem formed by the

vascular cambium during one growth season

• Early Spring wood – vessel diameter is large, xylem walls are thinner

• Late Summer wood – vessel diameter is small, walls are thicker

• Tropical trees:have no annual rings, because seasons are so similar

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Vascular tissue: Trees• Vascular tissue is located on the

outer layers of the tree.

wood

_______

________

bark

Vascularcambium

copyright cmassengale

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Gymnosperms• Conifers are most important group of

gymnosperms• Largest and most familiar group• Bare seeds in cones• Staminate cones – male cones• Ovulate cones – _________ cones• Seeds produced on an open scale• (Do not produce flowers

or fruit)

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Gymnosperms• Mainly woody plants that include• Oldest living trees: bristlecone pine,

5000 yrs old!• Most massive trees

(giant sequoia): up to 375 ft. tall, 41 ft wide!

• Tallest living trees (redwoods)

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Conifers• Conifers adapted to temperate to cold

regions• Narrow leaves (needles) help to

conserve water• Covered by resins – for protection

from predators, fire, etc.

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Other gymnosperms

• Cycads – short shrubs,native to tropical regions (look like palms)

• Ginkgo biloba – a “living fossil”, male and female tree,used as a medicinal plant

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Other gymnosperms

• Welwitschia – a bizarre gymnosperm plant that grows in Namib desert (So. Africa).

• Live up to 2000 years in these extreme conditions!

• Only makes two leaves throughout its life. It takes water from sea mist

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Significance of gymnosperms

• Ecological importance:• Provide food and habitat for wildlife• Forests prevent soil erosion• Reduce greenhouse-effect gasses• Economic and commercial importance:• Lumber for wood, paper, etc.• Resins – wood, furniture, etc.• Ornamental plants (trees, landscaping)• Food – pine nuts (pesto, etc.)

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ANGIOSPERMS

• Angiosperm means “covered seed”• Have flowers • Have fruits with seeds• Live everywhere – dominant plants in

the world• 260,000 species (88% of Plant

Kingdom)• Angiosperms are the most successful

and advanced plants on earth

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Evolution of Angiosperms• Advancements over gymnosperms:• Angiosperms have flowers – many use

pollinators• Fruits and seeds – adapted for dispersal• Double fertilization of the endosperm in

the seed

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Angiosperm life cycle• Flower has male and female sex

organs

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Flower structure• Male sex organs: Stamens, composed of

anther – organ that produces pollen (male gametophyte)

• Female sex organs: The carpel• Ovary is the enlarged basal portion of carpel

that contains the ovules (female gametophyte)

• The stigma is the receptive portion ofthe carpel for pollengrains to adhere

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Flower structure

• Non-reproductive parts:• Sepals (green) are the

outermost whorl of leaf-like bracts

• Petals (usually colored) are the inner whorl of leaf-like bracts

• Both can have various shapes and colors

• Tepals -_______________

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Angiosperm life cycle• Heterosporous: forms two different

types of spores (micro- and megaspores; male and female spores)

• Male – pollen grains contain tube nucleus and generative cell (2 sperm nuclei)

• Female – female gametophyte contains egg and 2 polar nuclei

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Angiosperm lifecycleFlowering plants

exhibit alternation of generations. The large, familiar flowering plant is the diploid sporophyte, while the haploid gametophyte stages are microscopic. The unique feature about the life cycle of flowering plants is a double fertilization that produces a diploid zygote and a triploid endosperm or nutritive tissue.

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Double fertilization• Pollen grain germinates on stigma

forming a pollen tube, which grows down style to the ovary

• Pollen has 2 haploid sperm nuclei, which travel to the ovary

• One sperm nucleus fertilizes the haploid egg forming the 2n zygote

• Another sperm nucleus unites with the 2 polar nuclei, forming the triploid (3n) endosperm

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Seeds• Fertilized egg grows into a ___________,

which grows into plant embryo• Endosperm is stored food tissue – for

the embryo to grow • Mature ovule becomes the seed coat

and/or fruit

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Monocot vs. dicot

• Angiosperms are divided into monocots and dicots

• As the zygote grows into the embryo, the first leaves of the young sporophyte develop and are called as cotyledons (seed leaves)

• Monocots have one cotyledon (corn, lily, etc).

• Dicots have two cotyledons (bean, oak, etc).

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Comparing monocot vs. dicot plants

FEATURE MONOCOTS DICOTS

Cotyledons 1 2

Leaf venation

parallel broad

Root system

Fibrous Tap

Number of floral parts

In 3’s In 4’s or 5’s

Vascular bundle position

Scattered Arranged in a circle

Woody or herbaceous

Herbaceous Either

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Monocot vs. dicot• Number of cotyledons: one vs. two

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Monocot vs. dicot

• Leaf venation pattern: • Monocot is parallel• Dicot is net pattern

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Monocot vs. dicot root

• Monocot: Fibrous root

• Dicot: Tap root

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Monocot vs. dicot• Flower parts:

• Monocot: in groups of three

• Dicot: in groups of four or five

copyright cmassengale

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Monocot vs. dicot

• Vascular bundle position:

• Monocot: _____________

• Dicot: arranged in a circle

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Monocot vs. dicot• Stem type:

• Monocot: Herbaceous

• Dicot: herbaceous or woody

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Summary: Monocot vs. dicot

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Seed plants (Ch.30)

protected gametophytes

advantages of seeds gymnosperms

angiosperms

monocots

eudicots

Fig. 30.2 Notice how the importance of the gametophypte dwindles as we move from mosses to ferns to seed plants. The gametophyte of a seed plant is microscopic and not green (does not carry out photosynthesis)

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Seed plants (Ch.30)



angiosperms

monocots

eudicots

Lots of specialized terms are used to describe the life cycle of see plants. Here, we will use the fewest we can, and simply drastically. Fig. 30.3.

This whole structure is a ovule (integument, the cells of the megasporangium, and the cells of the megaspore). The megaspore is formed by meiosis, so is a haploid gametophyte, the rest is diploid sporophyte.

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Seed plants (Ch.30)



angiosperms

monocots

eudicots


One of the female gametophyte cells becomes an egg (n). The rest divide to produce the rest of the cells of the female gametophyte. A male gametophyte (n), or pollen grain, enters the ovule, and the nucleus of one of its cells acts like a sperm, and fertilizes the egg (= zygote).

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Seed plants (Ch.30)



angiosperms

monocots

eudicots


The haploid female gametophyte (minus the cell that became the egg) becomes a mass of tissue that will provide a food supply for the new embryo developing from the zygote. The integument becomes a hard seed coat. Note that the embryo stops developing until it germinates - thus the “baby plant” in a peanut!

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Seed plants (Ch.30)



angiosperms

monocots

eudicots

The advantages of seeds are pretty obvious - there is no need for the gametophyte to live in a damp place so sperm can swim to the egg - seed plants can, and do, live everywhere.

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Seed plants (Ch.30)



angiosperms

monocots

eudicots

Gymnosperms are seed plants that do not have a fruit around the seed, and thus have “naked seeds”. Most of us think of gymnosperms as just “pines” (or conifers), but there is quite a diversity. Ginkos live on campus - have you seen one? The “fruit” is not really a fruit, but part of the ovule..

pine

gingko

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Seed plants (Ch.30)



angiosperms

monocots

eudicots

Angiosperms do not have naked seeds, but seeds surrounded by a n extra layer of tissue that forms a fruit (which may be juicy or dry). Fig. 30.8, 30.9

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Seed plants (Ch.30)



angiosperms

monocots

eudicots

But of course, angiosperms also have flowers! Fig. 30.7. You do not have to memorize all the parts, but know that that most flowers have both male, pollen producing parts, and female ovules.

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Almost all angiosperms fall naturally into two groups, monocots (one cotyledon, or seed leaf) and dicots (two cotyledons). A few dicots don’t form a clade, but the huge majoroty that do are called true dicots, or eudicots. Fig. 30.12 (p. 603)

Seed plants (Ch.30)



angiosperms

monocots

eudicots

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Fig. 30.13. Angiosperms and animals have evolved very intricate mutualistic interactions involving pollination - interactions that benefit both.

Seed plants (Ch.30)



angiosperms

monocots

eudicots

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Land Plants I- how land plants colonized land (Ch. 29)

Land plants evolved from green algae; terrestrial adaptations; alternation of generations; bryophytes dominated by gametophyte generation; ferns dominated by sporophyte

Learning goals: Lecture 3, Biological Diversity (Plants and Fungi)

Readings: Chapters 29, 30, and 31 (read all of these, but the parts covered in lecture are most likely to be on a test ).

Land plants II - Seed plants (Ch.30)

Tiny gametophytes protected in ovules and pollen; advantages of seeds; Gymnosperms have “naked seeds”; Angiosperms have seeds in fruits; Monocots, Eudicots

Fungi (Ch. 31)

Characteristics; fungi reproduce by spores; fungal origins and relationships; importance

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Lecture 3 specific reading. The entire reading is Chapters 29, 30, and 31

Fig. 28.3, p. 568 – read just figure legends – note that comlex algae like Ulva seem very“plant-like”

Fig. 29.3. p. 574, Genetic EvidenceFig. 29.5, p. 576, (top), p. 576, (also p. 574, Adaptations enabling the move to land.Fig. 29.5 (bottom), p. 576, Alternation of generationsFig. 29.8, p. 581, also p. 580, Bryophyte gametophtesFig. 29.12, p. 585Fig. 29.14, p. 587, take a look at the club moss and horsetail photos, similar to one shownin lectureFig. 29.15, p. 588, read Significance of seedless vascular plants (even though notdiscussed in lecture)

Fig. 30.2, p. 592Fig. 30.3, p. 593, also p. 592 Ovules and Production of Eggs, Pollen and Produciton ofsperm, p. 593, the Evolutionary advantages of seedsFig. 30.7, p. 598, FlowersFig. 30.8, p. 598, p. 598-599, FruitsFig. 30.9, p. 599, more fruits.Fig. 30.12, left side, p. 603, focus on cotyledons and leaf venation, but read all charctersthat distinguish monocots and dicots.Fig. 30.13, p. 604

Fig. 31.2, p. 609Fig. 31.6, p. 611Fig. 31.7, p. 611Fig. 31.5, p. 611. If you want to understand about the heterokaryotic stage, you maywant to read p. 610-611, Sexual reproductionFig. 31.23, p. 621-622, LichensFig. 31.25, p. 622-623, PathogensFig. 31.26, p. 623, Practical Uses of Fungi

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Pine Life-Cycle

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male or pollen cone

Female or ovulate cone

pollen cone

ovulate cone

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male cone

microsporophyll

microsporangium

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female cone

scale “megasporophyll”

ovule .megasporangium

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scale

seeds

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Yew

Coniferophyta

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Bristlecone Pine

Coniferophyta

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Giant Redwood

or

Sequoia

Coniferophyta

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Spruce

Hemlock

Coniferophyta

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Fir

Douglas Fir

Coniferophyta

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Cycadophyta: cycads

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Ginkgophyta:

Ginkgo biloba

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Gnetophyta:

Ephedra mormon tea

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Gnetophyta:

Gnetum

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Gnetophyta:

Welwitschia

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Leaves: Many different sizes, shapes. (Pine needles, cabbage, oak, etc.)

* Capture sun’s energy for photosynthesis* Structure of a leaf:

- Upper surface cells- Chloroplasts- Veins with xylem and phloem- Underside surface cells- Stomata (“stoma” in Greek means “mouth”,

opening)

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The Structure of a Leaf

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Cuticle

Upper Epidermis

Palisade mesophyll

Vascular Bundle

Spongy mesophyll

Lower Epidermis

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VENATION

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Transpiration = process of evaporation from leaves.

* Too much evaporation and the plant shrivels and dies* Closing the stomata helps slow down transpiration.

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Stems: support the plant and carry substances between the roots and leaves.

* Some stems also store food (starches) like in asparagus.

* They vary in size and shape:- Boabab tree has a huge stems.- Cabbage have short, hidden stems.

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* Structure of stems:

- Herbaceous (soft) [dandelions,tomato plants]

- Woody (hard) like trees and rose bushes

- Both have xylem and phloem, but woody stems have extra layers:

Outer BarkInner Bark (phloem)Cambium (to produce new phloem and

xylem)Sapwood (active xylem - still transporting)Heartwood (inactive xylem); just gives

strengthPith (center storing food & water in young

trees)

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Parts of a Woody Stem

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Annual Rings = xylem rings

* Spring Xylem is wide & light brown (grows rapidly)* Summer Xylem is thin & darker (grow slower)* Each pair of light & dark rings = one year’s growth.

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Roots: (Anchors. Absorbs water & nutrients from soil)

* Two Types1. Taproot = deep into soil2. Fibrous Roots = several branching main

roots

* Root structure- Root Cap the rounded tip containing

dead cells.- Root hairs increase surface absorption

area - Cambium produces xylem and phloem

tissues.- Xylem transports substances up to the

plant- Phloem brings food down to the growing

root

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Tap RootFibrous Roots

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Root:

InternalStructure

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Roots do not absorb water and minerals through a smooth Epidermis. Tiny, hairlike projections called ROOT HAIRS on the epidermis absorb water and dissolved minerals from the soil. Root Hairs also INCREASE the Surface Area of the Plant Roots.

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Dicot Root Monocot Root

Epidermis

Cortex

Pith

Xylem

Phloem

Endodermis

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Gymnosperms

Gymnosperm = seed plant that produces naked seeds.

* Many have needlelike or scalelike leaves and deep root systems.

* Note the book says fossils indicate there were many more gymnosperms in the past than today. This is because the global flood 4,000 years ago wiped out many plants.

(The dates given by many books of millions of years are false guesses. See the booklet by Dr. Humphreys.)

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Types of Gymnosperms:

- Cycads (look like palm trees with large cones)

- Ginkgo (only the Ginkgo biloba survives today)

- Gnetophytes (found only in deserts

- Conifers (largest & most common, pines, cedars, etc.)

[Conifers are evergreens: keep needles all year]

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Oldest living organism – Bristlecone Pine About 4,000 years old = just after Noah’s Flood.

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Reproduction of Gymnosperms:

* Cones – covered in scales, both male and female cones are produced.

- Pollen is produced by male cones, and pollen are tiny cells that later become sperm cells.

- Ovule is a structure containing an egg cell. Pollination = transfer of pollen from male structure to female part. (Pollen falls from a male cone to a female cone and fertilizes an ovule, which develops into a seed, with the zygote as the embryo part of the seed. It can take two years for seeds to mature, then the cones open & wind carries the seeds off.)

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The Life CycleOf a

Gymnosperm

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Angiosperms

Angiosperms – Two characteristics: 1. flowers 2. fruit

(To remember, think: “Angie” likes flowers, but “Gym” does not.)

* They produce seeds inside a fruit.

* Flower = angiosperm reproductive structure

* Fruit starts as an Ovary = where the seeds develop

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Flower Structure: Not all flowers have same parts. Some have only male parts.

* Sepals = leaf-like structures covering a bud.

* Petals = colorful structures of an open flower.

* Stamens = male parts (stalks topped by knobs)

* Pistils = the female parts in the center of the flower.

- Stigma = sticky tip of the pistil- Style = tube connecting stigma to ovary.

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The Structure of a Flower

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Filament

Anther

Stigma

Style

Ovary

Receptacle

Petal

Sepal Ovule

Flower Structure

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Life CycleOf anAngiosperm

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Reproduction of Angiosperms:

* Pollination = Pollen falls on a stigma when wind, bees, or bats carry it. (Sugar-rich nectar in the flower attracts bees or bats.)

* Fertilization = sperm & egg join together in the flower’s ovule.

- The zygote develops into the embryo part of the seed.

- The ovary around the seed develops into a fruit.(Apples, cherries, tomatoes, squash, etc. are all

fruit.)

* Dispersal – animals eat the fruit and the seeds come out the other end.

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Two types of Angiosperms:

1. Monocots – have only one seed leaf (cotyledon)(grasses, corn, wheat, rice, lilies, tulips)(flowers have either 3 petals or a multiple of 3

petals)(long slender leaves with veins parallel like train

rails)(vascular tissue scattered randomly in the stem)

2. Dicots – have two cotyledons(roses, violets, plus oak, maple, bean, and apple

trees)(flowers have 4 or 5 petals or multiples of these

numbers)(leaves are wide, with veins branches off one

another)(vascular tissue bundles arranged in a circle)

Angiosperms are used for food, clothing (cotton), Michael’s medicine (digoxin)

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Seed Structure Examples:

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Plant Responses and Growth

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Tropism = a plant’s growth response toward or away from a stimulus.* Positive tropism is when it grows toward a stimulus.* Negative is when it grows away from it.* Stimuli can be light, touch, and even gravity.

- Touch (thigmotropism) [vines coil around anything they

touch.]- Light (phototropism)

[leaves, stems, etc, grow toward light.]

- Gravity (gravitropism)(Positive) roots grow toward gravity’s

pull(Negative) stems grow away from its

pull

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Hormones = a chemical that affects how the plant grows and develops, & make tropism possible.

* Hormones also control germination, formation of flowers, stems, and the shedding of leaves and ripening of fruit.

* Auxin is an important hormone that speeds up plant cell growth rate.

- If light shines on one side of a stem, auxin moves to the shaded side and causes that

side to grow faster so the stem bends toward the light as it grows.

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Life Spans of Angiosperms:

* Annuals = complete a life cycle in one year.(pansies, wheat, tomatoes, cucumbers, etc)

* Biennials = complete life cycle in two years.(Second year they produce flowers and

seeds.)(Parsley, celery, etc)

* Perennials = live for more than two years (Oak tree, honeysuckles, etc)(Roots and stems survive the winter)

1 Seed Plants Gymnosperms & Angiosperms. 2 Evolution Of Land Plants REMEMBER: Terrestrial plants...

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Transcript of 1 Seed Plants Gymnosperms & Angiosperms. 2 Evolution Of Land Plants REMEMBER: Terrestrial plants...