DIVERSITY OF LIVING THINGS (PLANTS)

DIVERSITY OF LIVING THINGS (PLANTS)

G9 Alpha and Delta – 2011Mr. ARNOLD, Rafael

CROSS-SECTION OF A LEAF

CONTROLLING GAS EXCHANGE AND WATER LOSS

For photosynthesis to occur properly there must be a perfect balance of materials.

-Carbon dioxide gas (enters the plant coming from the air)-Oxygen (moves out to the atmosphere from the leaves)-Water vapor (moves out to the atmosphere in a process called transpiration)

PHOTOSYNTHESIS

GAS EXCHANGE IS PERFORMED BY STOMATA

Stomata (singular: stoma) are little openings at the bottom of leaves.

Function: Gas exchange (carbon dioxide comes in and oxygen goes out) and water loss by transpiration.

For photosynthesis the plant needs enough carbon dioxide coming in through stomata but without losing too much water.

Stoma in tomato leaf shown via colorized scanning electron microscope image

A stoma in cross-section

STOMATA

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/G/GasExchange.html

http://click4biology.info/c4b/9/plant9.2.htm

PLANT TRANSPIRATION

MECHANISMS TO AVOID WATER LOSSIN EXCESS.

-The surfaces of leaves are covered by a cuticle (waxy protective layer) that prevents water loss.

-When the air is dry and/or hot the stomata can close.

-Stomata can open at night when there isless evaporation.

MORE MECHANISMS TO AVOID WATER LOSS IN EXCESS.

-Some plants have adaptations, for examplein cacti the spines are modified leaves thatloses little water (because of less surface area exposed) by evaporation. The photosynthesis occurs in the stem.

The leaves have been reduced to needles to reduce transpiration.

The stem is fleshy in which the water is stored.

The stem becomes the main photosynthetic tissue.

ADAPTATIONS TO AVOID LOSS OF WATER IN CACTI

http://click4biology.info/c4b/9/plant9.2.htm#5

PLANTS GROW THROUGHOUT THEIR LIFETIMES

-Plants grow as long as they live.

-It occurs when cells at the tips of roots and stems divide faster than the others.

-Plants roots and stems grow longer, thicker andbranch.

-Only stems grow leaves.

PLANTS GROW THROUGHOUT THEIR LIFETIMES

-Leaves grow from buds produced in plant'sstems.A bud is small protuberance on a stem or branch, sometimes enclosed in protective scales (modified leaves) and containing an undeveloped shoot, leaf, or flower.

http://en.wikipedia.org/wiki/File:Plant_Buds_clasification.svg

PLANTS WITH SOFT STEMS

Some characteristics:

-The stems and leaves die when the enviromental conditions are not favourable (too cold or too dry).

-They store carbohydrates in their roots.

-If the conditions are good (heat, water, sunlight new stems and leaves grow.

PLANTS WITH WOODY STEMS

Examples:-Trees-Shrubs

Characteristics:-They have tough stems that do not die eachyear.

-The stems grow thicker and longer.

-They develop a thick stem from xylem. Thisis wood.

-The growing tissues in woody stems are located near the outer surface of the stem, right under the bark (The older part of the plant is in the center of the trunk).

Mosses & Ferns

MOST MOSSES AND FERNS LIVE IN MOIST ENVIRONMENTS (3.2 – 92)

Plants species adapted to life on land

-Evidences indicate that life appeared on Earth 3.8 billion years ago.

Tiny singled-cell (unicellular organisms) and multicellular organisms lived in watery environments such as:

-Warm shallow seas-Deep ocean vents (opening permitting the escape of fumes (a liquid, a gas, or steam).-Ponds (A still body of water smaller than a lake).

Fossil evidence suggests that plant life did not appear on Earth until 475 million of years ago.

The ancestors of plants were the first organisms to move to land

Scientists believe they looked like green algae thatexist today.

Green algae and plants are autotrophs (producers = produce their own food by doing photosynthesis).

Their cells contain chloroplasts (where photosyntesis is done).

THE FIRST PLANTS

The place where we are now millions of years ago could have been a pond.

This pond contained:

-Tiny floating organisms that could photosynthesize (the Sun provided the light).

-Nutrients ( C, H, O, N, P, S)

The following facts occurred:

-The organisms reproduced and increased in number.

-The pond became crowded.

-Some of the organisms were pushed to the edges of the pond.

-After a period of dry weather the pond shrank.

-Some organisms were no longer in the water.

-The ones that survived started to live on land and became the ancestors of the first plants.

Scientists believe this process happened in millions of ponds during millions of years

Some differences between life on land and life in water faced by the first plants:

Disadvantages:-On land there is no water to support the plants body.-There is no water to avoid drying out.

Advantage:-Plenty of carbon dioxide.-Plenty of light from the Sun.

MOSSES AND FERNS

-Both probably evolved from algae that lived in the sea and in freshwater.

-Mosses are simpler than ferns in structure.

MOSSES

http://www.aquamoss.net/Introduction.htm

Mosses

http://www.davidlnelson.md/Cazadero/Mosses.htm

http://www.countrysideinfo.co.uk/moss_article/page2.htm

Leaves of moss


MOSSES (SOME CHARACTERISTICS)

-Their cells have a cell wall that provides support.

-Most cells have areas for storage of water and nutrients (vacuoles).

-They have simple structures that function as roots, stems and leaves.

These structures allow mosses to live on land while algae live only in the water.

MOSSES ARE NONVASCULAR PLANTS

Mosses don't have vascular tissue (xylem and phloem).

Water and dissolved nutrients move from cellto cell. This process is not very efficient so mosses can't be large.

Mosses cellsWater moves through cell to cell as mosses lack a vascular system


CAPSULES

http://www.sbs.auckland.ac.nz/uoa/science/about/departments/sbs/newzealandplants/mosses/

CAPSULES IN MOSSES SPOROPHYTES

FERNS ARE VASCULAR PLANTS

FERNS ARE PLANTS

FERNS ARE VASCULAR PLANTS

Consequence: They can grow bigger much bigger than mosses

FERNS REPRODUCE WITH SPORES

LIKE MOSSES FERNS NEED WATER TO REPRODUCE

Trunks may reach heights of 20 m.

Found in moist areas

on both North and South Islands in

New Zealand.

(photo, John Braggins)

http://www.sbs.auckland.ac.nz/uoa/science/about/departments/sbs/newzealandplants/ferns/native-ferns/cyatheaceae-black-silver-ferns.cfm

FERNS

The stipes that support the large fronds are thick and very tough and have a characteristic black appearance. (photo, Larry Jensen)


FERNS

FRONDS OF FERNS


These structures are clusters. They are located on the back of the fronds. Spores are produced here by meiosis.http://www.sbs.auckland.ac.nz/uoa/science/about/departments/sbs/newzealandplants/ferns/native-ferns/cyatheaceae-black-silver-ferns.cfm

MOSSES, FERNS AND OTHER PLANTS CAN ALSO REPRODUCE

ASEXUALLY

• Small pieces can grow into a new plant• New plants can branch off from old ones

Comparing sexual and asexual reproduction

Asexual reproduction allows plants to spread more easily but the genetic material is exactly the same as the parent plant.Sexual reproduction increases genetic diversity and the possibility of new adaptations.

SEEDS AND SPORES ARE REPRODUCTIVE ADAPTATIONS

COMPARING SEEDS AND SPORES

SPORES

A spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions.Spores contain a single reproductive cellSpores are produced from meiosis in mosses and ferns.

SEEDS

A seed is young plant (embryo) contained in a protective coating containing nutrients.The coating protects the embryo until the conditions (moisture, temperature, water, etc) are good for it grow.

SOME CHARACTERISTICS OF SPORES AND SEEDS

GERMINATION

Germination is the growing of a new plant from:- A spore (a new plant will grow from a single cell)- A seed (a new plant will grow from an embryo).

GERMINATION IN SEEDS

An embryo can stay without growing for along time.

Germination is when the embryo starts togrow.

The embryo absorbs water from the soil and

uses the nutrients stored.

MORE COMPARISONS BETWEEN SPORES AND SEEDS

• Seeds can be spread by the wind, animals or water.

• Spores are spread by the wind in general.• Spores and seeds are adaptations that

made reproduction on land possible.

POLLEN

• Small multicellular structure containing a sperm cell.

POLLEN• They have a hard outer covering to keep

the sperm from drying out.

• They can be carried by:- Wind, water, animals (insects, birds,

butterflies, bats, etc)

POLLINATION

• The pollen grain attaches to the part of the plant that contains the egg.

• The sperm is released and gets to the egg.

Angiosperms

Seed Plants that produce Flowers and Fruits

Angiosperms

• Most species of plants are angiosperms;• Most trees whose leaves change color in

the fall;• Sperm protected in a pollen grain;• Eggs develop into embryos that are

enclosed within seeds;• Male and female parts may be on the

same plant or not.

Flowers are the Reproductive Structure of Angiosperms

• Sperm and egg cells are contained in a flower;

• Egg cells develop in a part of the flower called ovary;

• Once the eggs are fertilized seeds form and ovary wall thichens becoming a fruit!

Plants Also Reproduce Asexually

• New shoots can grow out from the parent plant;

• Asexual reproduction allows plants to reproduce even when the conditions are not right for the germination of seeds.

Strawberry new shoot – “runner

No Genetic Material Exchange! No Diversity!

Parts of a Flower

The pollen-bearing part of a stamen.

the stalklike portion of a stamen, supporting the anther.

The part of a carpel that receives the pollen

Extension of the carpel, which bears the stigma at its apex

The enlarged lower part of the carpel enclosing the ovules or young seeds.

The modified or expanded portion of the stem or axis that bears the organs of a single flower

Stigma + Style + Ovary = CARPEL

Inside Ovary there are Ovules

PETALS: One of the often brightly colored parts of a flower surrounding the reproductive organs

SEPALS: One of the separate, usually green parts forming the calyx of a flower

Fruit• A Fruit is a ripened plant ovary;• Ovaries may contain one or more seeds.

Fleshy Fruits“have juicy flesh”

Dry Fruits“have dry flesh and shell”

Animals Spread Pollen & Seeds

Wind PollinationA lot more pollen is produced!

DIVERSITY OF LIVING THINGS (PLANTS)

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