2 2.2 – Properties of WaterWater is a neutral molecule and found over 75% of Earth’s surfaceHowever, water is polar (a molecule in which the charges are unevenly distributed)
3 2.2 – Properties of WaterPolar molecules like water can attract each other – known as hydrogen bondingThis accounts for many of waters special properties
4 2.2 – Properties of WaterCohesion: attraction between molecules of the same substanceWhy drops of water form beads and why there is such a thing as surface tensionAdhesion: attraction between molecules of different substancesCauses the capillary action that draws water out of roots up into a plants stems and leaves
5 2.2 Properties of WaterWater also has a high heat capacity – takes a large amount of heat to cause the molecules to move fasterThis is why cells don’t overheat as they are carrying out the bodies processes – the water is drawing the heat out (sweat!)
6 Chapter 22: PlantsPlants have adapted so well to many environments that they dominate much of the surface of the planetInclude trees, shrubs, mosses, and even green algae!
7 22.1 – Characteristics of Plants Plants are:Kingdom PlantaeMulticellularEukaryotesHave cell walls with celluloseAutotrophs (photosynthesis)
8 22.1 – Characteristics of Plants The lives of plants center on the need for sunlight, gas exchange, water and mineralsSunlight: required for photosynthesis so they’ve developed broad, flat leavesGas exchange: require carbon dioxide and have to let go of oxygen, so they’ve developed special parts to deal with thisWater 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
9 22.1 – The History & Evolution of Plants Ancestors of land plants were water-dwelling without leaves and roots: today’s algaeAt first, algae was in Protista, but because they have cell walls and do photosynthesis, they are classified as plants
10 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.
11 22.2 Seedless PlantsAlgae: any photosynthetic eukaryote other than a land plantMostly aquaticAbsorb moisture and nutrients directly from their surroundingsOne of the first plants to evolve billions of years agoCan form colonies – how first plants probably arose
12 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 waterLack vascular tissue (roots and stems) and lignin, and therefore cannot support a tall plant bodyInclude mosses, liverworts, and hornworts
13 22.2 Vascular PlantsTracheophytes (vascular plants): have a transport system with true vascular (roots and stems) tissueCharacteristics:Contain cells called tracheids (water conducting cells)Contain xylem (carries water from the roots) and phloem (transports solutions of nutrients and carbs)
14 22.2 Vascular Plants Vascular plants are split up into 2 categories: Seed Plants: the majority of plants on earthSeedless plants: ferns, mosses and horsetails
15 Let’s Practice!Study Workbook A Pgs. 17 #1-4 and Pgs SKIP #4-6Work with a buddy – one sheet of paperQuestion AND AnswerYou’ve got 40 minutes!!
16 22.3 Seed PlantsEach and every seed contains a living plant ready to sprout as soon as it encounters the proper conditions for growthA seed is a plant embryo and a food supply, encased in a protective covering
17 22.3 The Importance of Seeds Unlike mosses and ferns, the gametes of seed plants do not need standing water for fertilizationAdaptations that allow seed plants to reproduce without standing water include:a reproductive process that takes place in cones or flowersthe transfer of sperm by pollinationthe protection of embryos in seeds
18 22.3 Seed Plants Gymnosperms Angiosperms Bear seeds directly on scales of conesMale gametophyte is in pollen grainPollen is carried by windFlowering plantsBear their seeds in flowers inside a layer of tissue to protect the seedMale gametophyte also in pollen grainPollen is carried by animals
19 22.3 Seed PlantsEmbryos can remain in dry conditions for weeks or even years because of the tough seed coat that surrounds and protects it
20 22.4 Flowering PlantsAngiosperms (flowering plants) are the most recent in evolution of plantsContain ovaries, which surround and protect seedsAttract animals such as bees to carry pollen to other flowers
21 22.4 Flowers & FruitsFruit contains one or more ovaries with seeds inside the wallsHelps to disperse the seeds, especially when eaten by an animalIncrease the range the plants inhabit (over hundreds of km)
22 22.4 Angiosperm Classification Classified according to the number of seed leaves (cotyledons) in their embryosOne seed leaf – monocotsTwo seed leaves – dicots** Recent classification has shown dicots go into a variety of different categories, and have been expanded**Figure is a good reference!