DIVERSITY OF LIVING THINGS G9 α ∆ Ω PLANTS CROSS-SECTION OF A LEAF http://en.wikipedia.org/wiki/Palisade_cell 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 http://en.wikipedia.org/wiki/File:Photosynthesis.jpg 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. STOMATA Stoma in tomato leaf shown via colorized scanning electron A stoma in cross-section microscope image http://en.wikipedia.org/wiki/Stoma http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/G/GasExchange.html PLANT TRANSPIRATION http://click4biology.info/c4b/9/plant9.2.htm MECHANISMS TO AVOID WATER LOSS IN 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 is less evaporation. MORE MECHANISMS TO AVOID WATER LOSS IN EXCESS. -Some plants have adaptations, for example in cacti the spines are modified leaves that loses little water (because of less surface area exposed) by evaporation. The photosynthesis occurs in the stem. ADAPTATIONS TO AVOID LOSS OF WATER IN CACTI 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. 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 and branch. -Only stems grow leaves. PLANTS GROW THROUGHOUT THEIR LIFETIMES -Leaves grow from buds produced in plant's stems. 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 examples: -Wildflowers -Garden flowers -Vegetables 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 each year. -The stems grow thicker and longer. -They develop a thick stem from xylem. This is 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 that exist 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) 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 (became smaller in size). -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 http://www.countrysideinfo.co.uk/moss_article/page2.htm http://www.countrysideinfo.co.uk/moss_article/page2.htm Leaves of moss http://www.davidlnelson.md/Cazadero/Mosses.htm 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 cell to cell. This process is not very efficient so mosses can't be large. Mosses cells Water moves through cell to cell as mosses lack a vascular system http://www.davidlnelson.md/Cazadero/Mosses.htm MOSS REPRODUCTION MOSS REPRODUCTION Life cycle of a moss http://www.sbs.auckland.ac.nz/uoa/science/about/departments/sbs/newzealandplants CAPSULES CAPSULES IN MOSSES SPOROPHYTES http://www.sbs.auckland.ac.nz/uoa/science/about/departments/sbs/newzealandplants/mosses/ FERNS ARE VASCULAR FERNS ARE VASCULAR PLANTS PLANTS FERNS ARE PLANTS Consequence: They can grow bigger much bigger than mosses FERNS REPRODUCE WITH SPORES LIKE MOSSES FERNS NEED WATER TO REPRODUCE FERNS REPRODUCTION FERNS REPRODUCTION FERNS 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) http://www.sbs.auckland.ac.nz/uoa/science/about/departments/sbs/newzealandplants/ferns/native- ferns/cyatheaceae-black-silver-ferns.cfm FRONDS OF FERNS http://www.sbs.auckland.ac.nz/uoa/science/about/departments/sbs/newzealandplants/ferns/ native-ferns/cyatheaceae-black-silver-ferns.cfm 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 COMPARING DOMINANT STAGES OF MOSSES AND FERNS • In mosses the dominant stage is male and female plants (the ones producing sperms and eggs). • In ferns the dominant stage is the spore- producing plant. COMPARING FIRST AND SECOND GENERATIONS IN MOSSES AND FERNS In mosses and ferns: -The first generation are the structures that produce sperms and eggs. -The second generation is the structure that produces the spores 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 cell Spores 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 a long time. Germination is when the embryo starts to grow. 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) Tip of a tulip stamen with many grains of pollen POLLINATION • The pollen grain attaches to the part of the plant that contains the egg. • The sperm is released and gets to the egg. Life cycle of a pine tree The reproductive structures are pinecones Mature female European Black Pine cone http://en.wikipedia.org/wiki/File:Pinus_nigra_cone.jpg Male cone of a pine http://en.wikipedia.org/wiki/Pine_cones Each tree has separate male and female cones. Sperm and eggs are produced by meiosis in the cones. Gymnosperms are Seed Plants “naked seed” • Pollen and Seeds are reproductive adaptations; • Seed Plants are generally better at reproducing in “difficult” environments, like dry and cold; • GYMNOSPERMS produce seeds, but they are not enclosed in fruits! Conifers “most common gymnosperms” • Are adapted to cold climates – little water available; • Leaves are needle-shaped and have a thick cuticle (prevents water loss); • Sugar production the whole year. Cycads, Gnetophytes & Ginkgoes “Other Gymnosperms” • These are 3 types of Gymnosperms which are very different from one another. Cycadophyta Equistella Cycads • Palm-like trees from tropical areas; • Produce Cones for Seeds; • Many produce poisonous compounds. Gnetophytes • Tropical Gymnosperms that produce cones; • Chemichals are used to treat cold symptoms. Ginkgo • Gymnosperms with fleshy seeds hanging from their branches; • Often in parks and along streets; • Seed coat produces a foul smell. 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 SEPALS: One of the separate, usually green parts forming the calyx of a flower PETALS: One of the often brightly colored parts of a flower surrounding the reproductive organs 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 Animals Spread Pollen & Seeds Wind Pollination A lot more pollen is produced!