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Complex Plants:. Chapters 22, 23 and 25. 22-1 Seed Plants. Benefits to plants of living on land are: 1. Abundant Sunlight for Photosynthesis 2. Free movement of carbon dioxide and oxygen. Problems encountered by life on land are:. Water and nutrients available only from the soil.
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Complex Plants: Chapters 22, 23 and 25
22-1 Seed Plants • Benefits to plants of living on land are: 1. Abundant Sunlight for Photosynthesis 2. Free movement of carbon dioxide and oxygen
Problems encountered by life on land are: • Water and nutrients available only from the soil. • Evaporation • Tissues must be held upright • Reproduction must occur without water.
Seed plants – designed for life on land Seed plants exhibit numerous adaptations that allow them to survive the difficulties of life on land. They evolved a variety of new adaptations that enabled them to live where ferns and mosses could not.
II. Roots, Stems, Leaves A. The three main organs in a plant are roots, stems and leaves. Roots perform three jobs: • absorb water and nutrients. • anchor plants • hold plants upright B. Stems hold a plants leaves up to the sun. C. Leaves are vital to the process of photosynthesis.
III. Vascular Tissue Tall plants face a challenge, water must be lifted from roots to leaves and compounds produced in leaves must be sent to the roots. A. Xylem is responsible for carrying water and nutrients up. They have thick cell walls so also provide strength to the woody parts. B. Phloem carries the products of photosynthesis from one part of the plant to another.
IV. Reproduction Free From Water • The seed plants you see around you are members of the sporophyte generation. • Flowers and cones are the reproductive structures where the gametophyte generation of the seed plant develops. • Male gametophytes are called pollen grains. Pollen grains are carried to the female gametophyte so no water is required. • Seeds protect the zygotes of seed plants. They are surrounded by a seed coat so can wait until conditions are right
23-5 Leaves The leaves of green plants are the world’s oldest solar energy collectors. Leaves are also the world’s most important manufacturers of food.
I. Leaf Structure A. Leaves consist of two parts: the blade and the petiole. • Blades are adapted to the specific environments in which the live. • Leaves contain specialized tissues such as: 1. Epidermal Cells 2. Inner layers of parenchyma cells 3. Vascular tissues
II. Epidermis: Controlling Water Loss • Epidermal cells are tough and do not contain chloroplasts. Together with the Cuticle, this layer protects delicate leaf tissues by slowing down the loss of water through evaporation. B. BUT, plants still need to “breathe” just as we do. They need to: 1. Exchange CO2 for O2 during photosynthesis. 2. Exchange O2 for CO2 in order to function (like us). Cellular respiration
C. Leaves must stay moist to carry out these gas exchanges. Seed plants solve this problem by balancing their need for gas exchange with water conservation. They use small openings called stomata. Stomata are generally located on the undersides of leaves.
D. The specialized cells on either side of a stoma are called guard cells. When water pressure is high, the cells are forced into a curved shape, opening the stoma. When water pressure is low, the cells spring together and close the stoma. E. Each type of plant has guard cells that balance water loss against the need for CO2.
III. Vascular tissues: The Veins of a leaf • Vascular tissue in leaves is directly connected to the vascular tissues of stems. In monocot leaves, veins run parallel. In dicot leaves, they have different patterns.
25-1 Cones & Flowers as Reproductive Organs • Introduction • Sexual Reproductive Organs 1. Gymnosperms have cones 2. Angiosperms have flowers
B. Review: Plant Life Cycles 1. Two generations a) diploid (2n) sporophyte b) haploid (1n) gametophyte which produces male and femalegametes 2. Fusion of gametes forms a zygote that grows into the next generation, the sporophyte
C. Sizes in Seed Plants 1. Dominant generation (the one that is large & obvious) = sporophyte 2. Gametophyte is hidden in the cones/flowers D. Advantages of Cones/Flowers 1. Enable seed plants to reproduce without standing water 2. An adaptation that helps them survive: the dry conditions of life on land
22-2 Evolution of Seed Plants I.Gymnosperms Gymno means naked, sperm means seed. There are three classes of gymnosperms: • Cycads • Ginkgoes • Conifers
Reproductive structures are called cones. Male cones produce male gametophytes called pollen. Female cones produce female gametophytes called eggs
from …..25-1 Cones & Flowers as Reproductive Organs II. Life Cycle of Gymnosperms A. Pine Tree Example 1. Tree grew from a zygote contained in a seed 2. It is the diploid(2n) sporophyte generation 3. Seedling matures, makes two types of cones: a) Male: contain microsporangia that produce pollen (male gametophyte) b) Female: contain megasporangia that produce ovules (female gametophyte)
B. Process • Pollen grains (from male cones) carried by wind 2. Female cones make a sticky secretion that traps pollen 3. Grain splits open, grows a pollen tube, which contains sperm • Pollen tube grows into the ovule, located in female cone • Sperm break out of the tube and fertilize egg in the ovule • Zygote grows into an embryo 7. Embryo is encased in a package; now called a seed a) seed = embryo plant + food supply for growth
from….. 22-2 Evolution of Seed Plants • Angiosperms • These are flowering plants. They reproduce sexually through their flowers in a process called pollination. Angiosperm seeds are contained within a protective wall that develops into a fruit.
from ….. 25-1 Cones & Flowers as Reproductive Organs III. Structure of a Flower A. Typical Flower 1. produces both male and female gametes B. Other ‘strategies’: 1. specialized male and female flowers on same plant (e.g. corn) 2. male and female flowers on separate plants(e.g. willow) C. Flower Parts 1. Are specialized leaves 2. Arranged in circles 3. Four kinds
IV. Pollination A. Definition: the transfer of pollen from anther to stigma B. Two types: 1. Self-pollination: when pollen comes from the same flower 2. Cross pollination: when pollen comes from a different plant C. Most plants cross-pollinate, which increases variation in their offspring Animation
VIII. Fertilization • Process 1. Pollen grain lands on stigma of same species 2. Pollen tube grows down the style, following a chemical trail 3. Tube reaches ovaryand enters the ovule 4. Inside pollen tube are two sperm nuclei (Note: no tails needed; don’t need propel themselves!) a) one sperm fuses with egg to form the zygote b) other sperm fuses with spare female nuclei to form endosperm (3N) • Endosperm = food source for baby plant Click for animation
B. Ecological Importance 1. Endosperm is rich in important nutrients • Examples: grass endosperm: corn, wheat, rice • After fertilization 1. Outer parts of ovule toughen into seed coat 2. Ovary wall thickens, merges with other parts to become fruit • Plants may use bright colours and sweettastes to make fruit attractive to animals Fruit Formation
IX. Formation of Seeds • The evolution of seeds was: a major factor in the success of angiosperms on land • Seeds assist embryos by providing: 1. nourishment 2. protection C. Structure 1. Cotyledon= seed leaf; they contain stored food that is used when seed germinates a) monocots (e.g. corn) have one b) dicots (e.g. beans) have two 2. Seed coats: Function: to protect seed from a) environment: (e.g. dryness, salt water) b) animal teeth, digestive chemicals
D. When animals eat seeds: • They germinate after their trip through the digestive tract • Animal waste acts as fertilizer • Usually deposited some distance away from where fruit was eaten 4. Reduces competitionbetween adult (plant) and offspring (seeds)
25-2 Seed Development I. Germination A. Process: 1. Water absorption causes endosperm & cotyledonsto swell 2. seed coat cracks open 3. Radicle emerges; grows into primary root 4. Growing shoot pushes up through soil
III. Seed Dormancy A. Definiton: A period during which the embryo is alive but not growing B. Purposes: 1. A long time required for dispersal a) e.g. coconut 2. To wait until environmentalconditions will support plant growth a) e.g. plants from temperate regions; dormant in winter, germinate in spring
22-3 Coevolution of Flowering Plants and Animals • Coevolution: the process by which two organisms evolve structures and behaviours in response to changes in each other over time. • The first flowering plants evolved at about the same time as the earliest mammals, shortly after birds and a while after the earliest insects. • Evolution of angiosperms with modern insects, birds and mammals is very important.
I. Flower Pollination • Wind: small, plain simple flowers with little or no fragrance. • Birds, insects, mammals: carry pollen from one plant to another. 1. Plants provide food in the form of pollen or nectar. 2. Animals provide direct transportation between male and female gametophyte.
II. Seed Dispersal The process of distributing seeds away from parent plants. There are 2 reasons for dispersal: 1. Prevent competition with parent plants for resources. 2. Colonize new environments