Chapter 2 Lesson 1

Levels of organization for organisms:organism – highest level of organization

organ system – group of different organs working together to do a job

organ – group of tissues working together to do a job

tissue – group of cells working together to do a job

cell – the lowest level of organization in a living thing

Levels of organization in a plant:

Remember plants have two organ systems:

1. Root system = roots

2. Shoot system = stems, leaves, and flowers

Root system

Shoot system

Plant organs:• Roots – anchor, absorb, store food• Stem – transports and supports• Leaves – photosynthesis; provide food• Flower – reproductive

Plant Organs

Leaves

•Lord has created a great variety of leaves.

Parts of a broadleaf:1. Blade - Flat surface of

the leaf

Leaves

•Lord has created a great variety of leaves.

Parts of a broadleaf:1. Blade

Flat surface of the leaf

2. Margin – outer boundary of the leafmargins are either toothed, entire, or lobed

ENTIRE

Leaves:•Lord has created a great variety of leaves.

Parts of the leaf:1. Blade2. Margin

3. Veins •add support to act as a skeleton•carry sap throughout the blade•Main vein in a pinnate leave is called the midrib

Midrib

Parts of the leaf:1. Blade2. Veins3. Margin

4. Petiole attaches blade to stemcontains vascular tissue to carry

sap through the stem to the blade

Parts of the leaf:1. Blade2. Veins3. Margin4. Petiole

Sessile leaves – leaves that do not have a petiole

grasses and other monocots leaf attaches to stem by way of sheath

4. Petiole

3 structures found where petiole attaches to stem:A. Stipule – one of a pair of appendages at the base of leaves

4. Petiole3 structures found where petiole attaches to stemA. Sepal

B. Bud •contains developing leaf or stem•Dormant in winter; brings forth leaf in spring

4. Petiole3 structures found where petiole attaches to stemA. SepalB. Bud

C. Bud-scale scars •markings on branch where bud previously existed •used for plant identification•Terminal bud leaves a ring,can tell the age of stem bycounting

Types of Leaves1. Simple leaves - have a single

blade on every petiole

Types of Leaves1. Simple leaves

2. Compound leaves midrib divides blade into leaflets compound leaves can be

identified by a stipule, bud, or bud-scale scar at the end where it attaches

4 Kinds of leaf arrangements:1. Opposite

• two leaves grow from a single node•node – where the leaf grows from the stem•ex. Maples

4 Kinds of leaf arrangements:1. Opposite

2. Alternate • one leaf grows from each node in an alternating pattern•ex. apple, oak

4 Kinds of leaf arrangements:1. Opposite 2. Alternate

3. Whorled •three or more leaves grow from a single node •ex. lilies

4 Kinds of leaf arrangements:1. Opposite 2. Alternate 3. Whorled

4. Rosette •cluster of leaves around the base of the plant •ex. dandelion

•Leaves are arranged at 90 degree angles for maximum sunlight

•Tropism – a plant’s growth response to a stimulus

3 Types of tropisms:

1. Phototropism • the ability of a plant to grow

toward to light

3 Types of tropisms:1. Phototropism

•How does phototropism occur? a. cells on the dark side of the stem grow longer than the cells on the light side of the stem b. this difference in growth is regulated by a grow hormone called auxin that is in greater quantity where there is lesser light

3 Types of tropisms:1. Phototropism

2. Geotropism – plant’s growth response to gravity

3 Types of tropisms:1. Phototropism 2. Geotropism

3. Thigmotropism – plant’s growth response to touch

Positive tropisms

•plant grows toward the stimulus

•Includes phototropism and the roots growing down in a geotropism

Negative tropism •plant grows away from the stimulus.•Includes stem growing away from center of gravity in a geotropism