PlantsMs. Luaces

Honors Biology

2.2 – Properties of Water

• Water is a neutral molecule and found over 75% of Earth’s surface– However, water is polar (a molecule in which the

charges are unevenly distributed)

2.2 – Properties of Water

• Polar molecules like water can attract each other – known as hydrogen bonding– This accounts for many of waters special properties

2.2 – Properties of Water

• Cohesion: attraction between molecules of the same substance– Why drops of water form beads

and why there is such a thing as surface tension

• Adhesion: attraction between molecules of different substances– Causes the capillary action that

draws water out of roots up into a plants stems and leaves

2.2 Properties of Water

• Water also has a high heat capacity – takes a large amount of heat to cause the molecules to move faster– This is why cells don’t overheat as they are carrying out the

bodies processes – the water is drawing the heat out (sweat!)

Chapter 22: Plants

• Plants have adapted so well to many environments that they dominate much of the surface of the planet– Include trees, shrubs, mosses, and even green algae!

22.1 – Characteristics of Plants

• Plants are:– Kingdom Plantae– Multicellular– Eukaryotes– Have cell walls with cellulose– Autotrophs (photosynthesis)

22.1 – Characteristics of Plants

• The lives of plants center on the need for sunlight, gas exchange, water and minerals– Sunlight: required for

photosynthesis so they’ve developed broad, flat leaves

– Gas exchange: require carbon dioxide and have to let go of oxygen, so they’ve developed special parts to deal with this

– Water and minerals: required for photosynthesis and survival, so they’ve evolved structures that limit water loss and increase the intake of water and nutrients upwards from the soil

22.1 – The History & Evolution of Plants

• Ancestors of land plants were water-dwelling without leaves and roots: today’s algae– At first, algae was in Protista, but because they have cell walls

and do photosynthesis, they are classified as plants

22.1 – The History & Evolution of Plants

• Over time, the demands of life on land favored the evolution of plants more resistant to the drying rays of the sun, more capable of conserving water, and more capable of reproducing without water.

22.2 Seedless Plants

• Algae: any photosynthetic eukaryote other than a land plant– Mostly aquatic– Absorb moisture and nutrients directly from their surroundings– One of the first plants to evolve billions of years ago– Can form colonies – how first plants probably arose

22.2 Mosses and other Bryophytes

• Bryophytes: higher degree of cell specialization and one of the first plants to become established on land.

• Characteristics:– Live in damp places with plenty of water– Lack vascular tissue (roots and stems)

and lignin, and therefore cannot support a tall plant body

– Include mosses, liverworts, and hornworts

22.2 Vascular Plants

• Tracheophytes (vascular plants): have a transport system with true vascular (roots and stems) tissue

• Characteristics:– Contain cells called tracheids (water conducting cells)– Contain xylem (carries water from the roots) and phloem

(transports solutions of nutrients and carbs)

22.2 Vascular Plants

• Vascular plants are split up into 2 categories:– Seed Plants: the majority of plants on earth– Seedless plants: ferns, mosses and horsetails

Let’s Practice!

• Study Workbook A Pgs. 17 #1-4 and Pgs. 253-255 SKIP #4-6

• Work with a buddy – one sheet of paper• Question AND Answer• You’ve got 40 minutes!!

22.3 Seed Plants

• Each and every seed contains a living plant ready to sprout as soon as it encounters the proper conditions for growth

• A seed is a plant embryo and a food supply, encased in a protective covering

22.3 The Importance of Seeds

• Unlike mosses and ferns, the gametes of seed plants do not need standing water for fertilization

• Adaptations that allow seed plants to reproduce without standing water include:– a reproductive process that takes place in cones or flowers– the transfer of sperm by pollination– the protection of embryos in seeds

22.3 Seed Plants

Gymnosperms• Bear seeds directly on scales

of cones• Male gametophyte is in pollen

grain• Pollen is carried by wind

Angiosperms• Flowering plants• Bear their seeds in flowers

inside a layer of tissue to protect the seed

• Male gametophyte also in pollen grain

• Pollen is carried by animals

22.3 Seed Plants

• Embryos can remain in dry conditions for weeks or even years because of the tough seed coat that surrounds and protects it

22.4 Flowering Plants

• Angiosperms (flowering plants) are the most recent in evolution of plants– Contain ovaries,

which surround and protect seeds

– Attract animals such as bees to carry pollen to other flowers

22.4 Flowers & Fruits

• Fruit contains one or more ovaries with seeds inside the walls– Helps to disperse the seeds, especially when eaten by an

animal– Increase the range the plants inhabit (over hundreds of km)

22.4 Angiosperm Classification

• Classified according to the number of seed leaves (cotyledons) in their embryos– One seed leaf – monocots– Two seed leaves – dicots– ** Recent classification

has shown dicots go into a variety of different categories, and have been expanded

– **Figure 22-22 is a good reference!