Algae were faced with challenge of life with little light.

zygote

SPOROPHYTE (2n)

GAMETOPHYTE (n)

GREEN ALGA BRYOPHYTE FERN GYMNOSPERM ANGIOSPERM

Evolutionary trend of plants started in the sea and moved slowly to wet lands and then to dry lands.

700 million years

Every plant around us today is a descendant of ancient species of green algae that lived in or near water and made it onto the land

Darwin’s theory: Evolution by Natural Selection

Peppered moth experiment of H.B.D.Kettelwell :

more of light-colored moths survived in unpolluted area. In soot-blackened areas, more dark-colored moths survived.

Overview of Plant BodyOverview of Plant Body

ShootShoot

RootRoot

Stem: Support leaves

Leaves: Photosynthesis

Flowers: Reproduction

Root: * Anchors plant

* Absorbs H2O

* Stores food

Three Types of Plant Tissues:

3) Ground Tissue - makes up bulk of plant body

2) Vascular Tissue - distribute H2O and solutes

1) Dermal Tissue - covers and protects

Where do these tissues originate from?

Meristem Tissues - Cells dividing constantly (mitosis)

- Two locations: * Apical

* Lateral

Shoot Apical Meristem divide to make new cells

Apical MeristemApical Meristem - - located in tip of stem and root- cells undergo mitosis and produce new cells

Root apical meristem divide to make new cells

As the new cells move away from tip, they elongate and form different tissues (maturation)

- increase plant length (primary growth)

Lateral MeristemLateral Meristem - located in vascular cambium and rings of cork cambium

- make new vascular tissue and new epidermis (cork)

- increases plant girth

Vascular cambium

Cork cambium

thickening

Three Types of Ground Tissue:- parenchyma - for storage

- sclerenchyma - for support

- collenchyma - for flexible support

SCLERENCHYMA

parenchyma cells• Thin cell walls

• Functions: photosynthesis, storage, secretion.

• Large central vacuoles filled with product of photosynthesis

• In plant roots that we eat: potatoes, radishes.

Sclerenchyma TissueSclerenchyma Tissue• Though, thick cell wall. Lignin makes cell water proof and strengthen cell wall ( this is what made plants stand on land) • Strengthen and support other plant tissues

• Two types: Fibers- next to vascular tissues. Ex. Cloth, rope, paper. Sclerid- star-shaped. Ex. Pear gritty texture, peach

pit.

PARENCHYMA COLLENCHYMA SCLERENCHYMA

Collenchyma Tissue• Uneven thickened cell wall with pectin ( this polysaccharide glues cellulose fibrils together & makes tissue pliable.

• Provides flexible support to stems and leaves.

SCLERENCHYMA

SCLERENCHYMACOLLENCHYMA

• Thin cell wall

• Storage & photosynthesis

• Uneven cell wall

• Flexible support

• Thick cell wall

• Strength and support

PARENCHYMA

Plant Ground Tissues

Two Kinds of Plant Vascular Tissue• Xylem

• Phloem

- Upward movement.- Dead at maturity.

- Carries H2O, dissolved nutrients.

- Carries products of photosynthsis.- Up and downward movement.- Alive at maturity

- Vessel Elements- pitted cell wall. Absence of end walls make water pipeline.

- Tracheids - pitted cell wall

- Sieve tube - perforated end walls - transport sugar

- Companion Cells- assist loading of sugars to various regions of plants

Vessels Tracheids

Sie

ve-t

ube

Companion cells

Two Kinds of Dermal Tissue• Epidermis - Single layered.

• Periderm - Multilayered cork replaces epidermis.

- For protection. - cuticle- a wax layer reduces water loss. - Epidermis/ from apical meristem

- For protection and reduction of water loss. - Bark/ from cork cambium

periderm

cork cambium

Plants are classified into 2 groups Plants are classified into 2 groups based on their seed based on their seed cotyledoncotyledon

Cotyledon is the leaf-like structure in seeds that store and absorb food for plant embryo.

• Monocotyledons (monocots) - one cotyledon

• Dicotyledons (dicots) - two cotyledons

Numbercotyledons

Numberflower parts

Vascular bundlearrangement in

stem

Leaf veinarrangement

DICOTSMONOCOTS

leaflike structure inseed; nourishes embryo

2

4s/5s ormultiplesof these

netlike

form ring

1

3s or multiple of 3

parallel

scattered

1

3s ormultiplesof 3

parallel

Numbercotyledons

Numberflower parts

Examples

2

lily, iris, tulip,corn, grass,orchids

netlikeLeaf vein

arrangement

DICOTSMONOCOTS

leaflike structure inseed; nourishes embryo

common trees,shrubs & flowers(oak, holly, rose)

4s/5s ormultiplesof these

Internal Structure of StemsInternal Structure of Stems

Monocot Dicot

Vascular bundle

Vascular bundle Epidermis

Cortex

Pith

Epidermis

Ground tissue

Arrangement of Vascular Bundles (VB) inMonocots and Dicots

vessels in xylem

vascular cambium

sieve tube companion cells

air space

sclerenchymafibers

Vessels

in xylem

sieve tube

companion cells Sclerenchyma

fibers

Monocot VB

Dicot VB

Structure of Vascular Bundle in Stem Structure of Vascular Bundle in Stem

epidermis

collenchyma

sclerenchyma

parenchyma

xylem

pholem

epidermis

collenchyma

sclerenchyma

paranchyma

phloem

xylem

External Structure of Roots:External Structure of Roots:Primary root - The first part to emerge from seedLateral root - perpendicular to primary root

Tap Root Fibrous Root