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Plants Unit 7 Chapters 22-25 Biology. Origin of Plants  Evolved from organisms similar to green algae  First evidence in the fossil record was around.

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Presentation on theme: "Plants Unit 7 Chapters 22-25 Biology. Origin of Plants  Evolved from organisms similar to green algae  First evidence in the fossil record was around."— Presentation transcript:

1 Plants Unit 7 Chapters Biology

2 Origin of Plants  Evolved from organisms similar to green algae  First evidence in the fossil record was around 500 million years ago  Did not have any leaves  Psilophytes – earliest known plant fossil

3 Plant Characteristics  A multicellular eukaryote  Produce its own food (glucose) by way of photosynthesis –Use chlorophyll (green pigment)  Thick cell walls made of cellulose  Cuticle – waxy waterproof coating on the stems and leaves

4 Needed for survival  Sunlight –Used in photosynthesis to produce food  Water and Minerals  Gas exchange –Require oxygen for cellular respiration and carbon dioxide for photosynthesis  Movement of water and nutrients –Use specialized tissues (vascular tissue)

5 Plant Life Cycle  Alternation of generation –Two alternating phases, a diploid phase and a haploid phase –Sporophyte  Diploid phase that reproduces by asexual spores –Gametophyte  Haploid phase that reproduces sexually by producing gametes that fuse together by fertilization

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7 Classification of Plants  4 groups that are based on: –Water-conducting tissues –Seeds –Flowers  Bryophyte (Nonvascular)  Ferns and allies (Seedless vascular )  Gymnosperm (Seed vascular)  Angiosperm (Seed vascular flowering plant)

8 Bryophytes  Nonvascular Plants  Life cycle depends on water for reproduction  Draws up water by osmosis  Include: mosses, liverworts, and hornworts

9 Bryophyte Types  Mosses –Most common bryophyte –Rhizoids – long, thin cells that anchor them in the ground and absorb water and minerals from the soil  Liverworts –Gemmae – small multicellular reproductive structures used in asexual reproduction

10 Bryophyte Life Cycle  Gametophytes –Dominant recognizable stage –Carries out most of the plant’s photosynthesis –Antheridia – produce the sperm (male) –Archegonia – produce the egg (female)  Sporophyte –Depends on the gametophyte for water and nutrients

11 Vascular Plants  Contain specialized tissue that conducts water and nutrients throughout the plant (vascular tissue)  Tracheids – tubular cells that are specialized to conduct water; dead at maturity  Xylem – transport subsystem that carries water upward from the roots  Phloem – transports solutions of nutrients and carbohydrates produced in photosynthesis –Sieve tube element – main phloem cells that are surrounded by companion cells

12 Vascular Plants  Roots – underground organs that absorb water and minerals  Stems – supporting structures that connect roots and leaves; carry water and nutrients between them  Leaves – photosynthetic organs that contain one or more bundles of vascular tissue (veins)

13 Ferns and Allies: Seedless Vascular Plants  Include club mosses, horsetails, and ferns  Ferns –Rhizomes – creeping or underground stems –Fronds – large leaves of ferns.  Life cycle of ferns –Diploid sporophyte is the dominant stage –Sporangia – tiny containers of haploid spores –Sori – group or cluster of sporangia

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15 Seed Plants  Divided into 2 groups –Gymnosperms  Bear their seeds directly on the surfaces of cones  Include: conifers, cycads and ginkgoes –Angiosperms (Flowering plants)  Bear their seeds within a layer of tissue that protects the seed  Include: grasses, flowering trees and shrubs, and all wildflowers and cultivated flowers

16 Adaptations of Seed Plants  Reproduce free from water by the use of: –Flowers and cones  Cones are the seed bearing structure of gymnosperms  Flowers are the seed bearing structures of angiosperms –Transfer of sperm by pollination  Pollen grain – tiny structure that contains the entire male gametophyte  Pollination – transfer of pollen to the female structure; can be transferred by wind, insects or small animals

17 Adaptations of Seed Plants –Protection of embryos in seeds  Seed – an embryo of a plant that is encased in a protective covering (seed coat) and food supply (cotyledons); may have structures that aid in its dispersal  Embryo – an organism in its early stage of development

18 Angiosperms – Flowering Plants  Flowers –Reproductive organ; contains ovaries that surround and protect the seed  Fruit –Wall of tissue surrounding the seed –Used to attract animals to disperse their seeds

19 Parts of a Flower  Sepals and Petals –Outermost floral parts that protect the developing bud –Petals – brightly colored to attract vectors  Stamens –Male reproductive part –Consists of a thin stalk (filament) and an oval sac that consist of pollen grains at the top (anther)  Pistil (carpels) –Female reproductive part –Consist of a broad base (ovary) that contain one or more ovules, the stalk that comes from the ovary (style), and a sticky portion at the top (stigma) where pollen grains land

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21 Diversity of Angiosperms  2 types: named for the number of cotyledons in the plants embryo –Monocots (monocotyledon)  Corn, wheat, lilies, orchids, and palms –Dicots (dicotyledon)  Roses, clover, tomatoes, oaks, and daisies

22 Comparison of Monocots and Dicots  Monocots –Single cotyledon –Parallel veins –Flower parts are multiples of 3 –Vascular bundles are scattered –Fibrous roots  Dicots –Two cotyledon –Branched veins –Flower parts are multiples of 4 or 5 –Vascular bundles are arranged in rings –Taproot

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24 Diversity of Angiosperms  Life spans are divided into 3 categories: –Annuals  Flowering plant that complete a life cycle within one growing season  Marigolds, petunias, and pansies –Biennials  Complete their life cycle in two years  Primrose, parsley, and celery –Perennials  Flowering plants that live for more than two years  Asparagus, many grasses, palm trees, maple trees, and honeysuckle

25 Seed Plant Structure  3 principal organs: –Roots  absorb water and dissolved nutrients  anchor plants in the ground  Protect the plants against bacteria and fungi  Hold plant upright against wind and rain –Stems  Transports nutrients between the leaves and the roots –Leaves  Photosynthetic systems of the plant

26 Seed Plant Structure  3 plant tissue systems: –Dermal tissue  Outer covering of a plant  Consist of a single layer of epidermal cells –Vascular tissue  transport system  composed of xylem and phloem –Ground tissue  Cells that lie between the dermal and vascular tissues  Functions in storage, adds flexibility and strengthens the plant

27 Plant Growth  Most plants have an open or indeterminate type of growth –i.e. they grow as long as they live  Meristems – clusters of tissue that are responsible for growth throughout the plants life  Meristematic tissue – undifferentiated cell that are produced by the meristems  Apical meristem – increase the length of stems and roots

28 Roots  Function: anchor the plant and absorb water and dissolved nutrients from the soil  2 main types of roots: –Taproot  Found mainly in dicots  Primary root is long and thick  Secondary roots remain small  Example: oak and hickory trees –Fibrous root  No single root grows larger than the rest  Help prevent erosion  Example: grasses

29 Roots  Root structure and growth –Root hairs – tiny cellular projections that increase the surface area through which water can be absorbed –Cortex – spongy layer of ground tissue underneath the epidermis –Root cap – protects the root as it forces its way through the soil

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31 Stems  3 important functions: –Produce leaves, branches, and flowers –Hold leaves up to the sunlight –Transport substances between roots and leaves  Nodes – point of leaf attachment  Internodes – regions between nodes  Buds – contain undeveloped tissue that can produce new stems and leaves

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33 Stems  Monocot and Dicot Stems

34 Stems  Growth of stems: –Primary growth – growth in which the plant increase in height; occurs at the apical meristems; takes place in all seed plants –Secondary growth – growth in which the stem increases in width; occurs in the lateral meristem  Vascular cambium – produces vascular tissue  Cork cambium – produces the outer covering of stems (bark)

35 Leaves  Structure is optimal for absorbing light and carrying out photosynthesis  Blade – thin, flattened sections of the leaf that is attached to the stem by a thin stalk (petiole)  Functions: –Photosynthesis, transpiration, and gas exchange

36 Leaves  Transpiration – the loss of water through the leaves  Gas exchange occurs in the –Stomata – porelike opening in the underside of the leaf –Each stoma consist of two guard cells that control the opening and closing of the stomata

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38 Transport in Plants  Capillary action –The tendency of water to rise in a thin tube –Adhesion – is the attraction between unlike molecules; property that causes capillary action

39 Plant Hormones  Auxins – stimulate cell elongation  Cytokinins – stimulate cell division (growth)  Gibberellins – produce dramatic increases in size in the stems and fruit  Ethylene – stimulates fruits to ripen

40 Plant Responses  Tropisms – plant responses to external stimuli –Gravitropism – plant responses to the forces of gravity –Phototropism – tendency of a plant to grow toward light –Thigmotropism – response of plants to touch

41 Plant Adapted for Specific Habitats  Xerophytes – plants that live in the desert biome  Epiphytes – plants that are not rooted in soil but grow directly on other plants


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