March 4, 2013 Q-2 Pg.Daily Goal: We will be able to explain why leaves on trees in Alaska might look different than leaves in Costa Rica.

Homework: Revise your test.Science Starter: 1.Where do plants get energy from?2.Where do animals get energy from?3.Name one rainforest plant adaptation that you learned about from your plant packet.

Table Group Point!Table Group Point!Where is Costa Rica?

Table Group Point!Table Group Point!Who can guess what Ms. Petersen’s favorite

flower is?

Table Group Point!Table Group Point!Do trees have a stem? (You have to explain

your answer.)

Table Group Point!Table Group Point!Tell me 33 things you know about leaves.

Function of leavesFunction of leaves

• Leaves trap light energy for photosynthesis.• Leaves produce sugar from photosynthesis• Leaves exchange gases.

Which gasses do leaves exchange? oxygen and carbon dioxide

Which gas do leaves produce?

oxygen

Leaf StructureLeaf StructureLeaf Width:

• Wider leaves catch more light energy.

• Thin leaves help get carbon dioxide from bottom to top of leaf quickly for photosynthesis.

Pros and Cons of Big LeavesPros and Cons of Big Leaves

Pro of big leaves:• Bigger leaves can do more photosynthesis

Con of big leaves:• Bigger leaves also lose more water through transpiration.

• Pine trees live in places that are cold and dry.

• Costa Rica is a rainforest. It has wide-leaved plants.

Why does that Why does that make sense?make sense?

Gas exchange Gas exchange • Leaves are designed to let carbon dioxide to

get to the layer of chlorophyll at the top of the leaf.

• They have small holes called stomata on the under surface.

Stomata – small openings in leaves that open and close at different times of the day to let in carbon dioxide and let oxygen out

When it is light the plant needs CO2 for photosynthesis so the stoma open.

StomataStomata

Table Group Point!Table Group Point!

Would stomata be more likely to be open during the day or at night? (Be prepared to

explain your answer.)

StomataStomata

Carbon dioxide

oxygenGuard cell

Provided plant is photosynthesising

Stomata positionStomata position

Guard CellsGuard CellsStomata are surrounded by guard cells.

Guard Cells – surround the stomata and control the size of the stomata’s opening to help prevent water loss.

Two Table Group Points!Two Table Group Points!

Think about the function of guard cells. Which structure of the eye are guard cells most like?

(Be prepared to explain your answer.)

Guard Cells and Transpiration

• Transpiration – letting water vapor out through the stomata

• Transpiration cools the plant down (like sweating).

• Guard cells control transpiration.

Critical Thinking!Critical Thinking!

What might happen if plants didn’t have guard cells or if the guard cells in a leaf weren’t

working?

Leaf diagram – palisade layer

CO2

Most chlorophyll

Epidermis and Cuticle• Just like humans

have an epidermis, or skin, plants also have an epidermis.

Epidermis – the outermost layer of a leaf

Leaf Cuticle

Leaf Cuticle – waxy layer on the outside of the leaf that helps prevent water loss

Why would the waxiness help Why would the waxiness help prevent water loss?prevent water loss?