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Unit 7 Plants

Unit 7 Plants. Ch. 22 Plant Diversity. What is a Plant?. Plants are multicellular eukaryotes that have cell walls made of cellulose They develop from multicellular embryos & carry out photosynthesis using the green pigments chlorophyll a & b. What Plants Need to Survive.

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Unit 7 Plants

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  1. Unit 7 Plants Ch. 22 Plant Diversity

  2. What is a Plant? • Plants are multicellular eukaryotes that have cell walls made of cellulose • They develop from multicellular embryos & carry out photosynthesis using the green pigments chlorophyll a & b

  3. What Plants Need to Survive • The lives of plants center on the need for light, water & minerals, gas exchange, & the transport of water & nutrients throughout the plant body

  4. What Plants Need to Survive • Plants use the energy from the sun to carry out photosynthesis • All cells require a constant supply of water, so plants must obtain & deliver water to their cells • Plants require oxygen for cellular respiration, & carbon dioxide for photosynthesis

  5. Early Plants • For most of Earth’s history, plants did not exist • The first plants evolved from an organism similar to the multicellular green algae living today

  6. Early Plants • The oldest known fossils of plants are almost 450 million years old, Cooksonia, a moss plant

  7. Overview of the Plant Kingdom • The plant kingdom is divided into 4 groups based on 3 features: water-conducting tissue, seeds, & flowers

  8. Overview of the Plant Kingdom • There are 235,000 flowering plant species, almost 90% of all living species of plants

  9. Bryophytes • Bryophytes - includes:mosses, liverworts, & hornworts, nonvascular plants • Bryophytes have life cycles that depend on water for reproduction • Lacking vascular tissue, they can draw up water by osmosis only a few centimeters above ground

  10. Groups of Bryophytes • Mosses are the most common, & grow in areas of water: swamps & bogs, etc. • They lack vascular tissue, which means they do not have true roots • Rhizoids - long, thin cells that anchor them in the ground & absorb water & minerals from surrounding soil

  11. Groups of Bryophytes • Liverworts are odd little plants that look like flat leaves attached to the ground, some species resemble the shape of a liver

  12. Groups of Bryophytes • Hornworts are generally found in soil that is damp nearly year-round

  13. Human Use of Mosses • In certain environments, dead sphagnum moss forms thick deposits of peat • Peat can be cut from the ground & burned as fuel, or used in gardening because it can improve the soil’s ability to retain water

  14. Seedless Vascular Plants • Vascular tissue - specialized to conduct water & nutrients throughout the plant

  15. Evolution of Vascular Tissue: A Transport System • Tracheids - thick cells that resist pressure, key cells in xylem • Xylem - transport system that carries water from roots to every part of a plant • Phloem - transports solutions of nutrients & carbs produced by photosynthesis

  16. Evolution of Vascular Tissue: A Transport System • Both forms of vascular tissue (xylem & phloem) can move fluids through the plant body, even against the force of gravity • Lignin - makes cell walls rigid, enables vascular plants to grow upright & reach great heights

  17. Ferns & Their Relatives • Seedless vascular plants that include: club mosses, horsetails, & ferns • Ferns have true roots, leaves, & stems • Roots - underground organs that absorb water & minerals • Leaves - photosynthetic organs that have 1 or more bundles of vascular tissue

  18. Ferns & Their Relatives • Veins - vascular tissue (xylem & phloem) gathered together • Stems - supporting structures that connect roots & leaves, carrying water & nutrients between them

  19. Club Mosses • Small plants that live in moist woodlands • The most common club mosses look like miniature pine trees, called “ground pines”

  20. Horsetails • Named because its stems look similar to horses’ tails • During Colonial times, horsetails were commonly used to scour pots & pans

  21. Ferns • Ferns have true vascular tissues, strong roots, creeping underground stems (rhizomes), & large leaves (fronds)

  22. Seed Plants • Seed plants are divided into 2 groups: gymnosperms & angiosperms • Gymnosperms - have their seeds directly on the surfaces of cones • Angiosperms - (flowering plants) - have their seeds within a layer of tissue that protects the seed

  23. Reproduction Free From Water • Adaptations that allow seed plants to reproduce without water include flowers or cones, the transfer of sperm by pollination, & the protection of embryos in seeds

  24. Reproduction Free From Water • Cones - the seed-bearing structures of gymnosperms • Flowers - the seed-bearing structure of angiosperms

  25. Reproduction Free From Water • Pollen grain - plant sperm • Pollination - the transfer of pollen from male reproductive structure to female reproductive structure

  26. Reproduction Free From Water • Seed - an embryo of a plant that is encased in a protective covering & surrounded by a food supply • Embryo - an organism in its early stage of development

  27. Reproduction Free From Water • Seed coat - surrounds & protects the embryo & keeps the contents of the seed from drying out

  28. Gymnosperms - Cone Bearers • Gymnosperms include: gnetophytes, cycads, ginkgoes, & conifers • Gnetophytes only have 2 huge leathery leaves, which grow continuously & spread across the ground

  29. Gymnosperms - Cone Bearers • Cycads are palm-like plants that reproduce with large cones, typically found in tropical places

  30. Gymnosperms - Cone Bearers • Ginkgo may be one of the oldest seed plant species alive today • Often planted around temples in China • Today, they are planted in urban areas where their toughness & resistance to air pollution make them popular shade trees

  31. Gymnosperms - Cone Bearers • Some conifers like the bristlecone pine tree can live for more than 400 years • Others like the giant redwoods, can grow to more than 100m in height

  32. Gymnosperms - Cone Bearers • Today, conifers thrive in a wide variety of habitats in several biomes • Most conifers are “evergreens” - they keep their leaves throughout the year

  33. Angiosperms - Flowering Plants • Angiosperms develop unique reproductive organs known as flowers • Flowers contain ovaries, which surround & protect the seeds • Fruit - a wall of tissue surrounding the seed

  34. Diversity of Angiosperms • Monocots & dicots are the 2 classes of angiosperms • They are named for the # of seed leaves, or cotyledons, in the plant embryo • Monocots - 1 seed leaf • Dicots - 2 seed leaves • Cotyledon - the first leaf or first pair of leaves produced by the embryo of a seed plant

  35. Characteristics of Monocots & Dicots

  36. Diversity of Angiosperms • There are 3 categories of plant life spans: annual, biennial, & perennial • Annuals - flowering plants that complete a life cycle within one growing season

  37. Diversity of Angiosperms • Biennials - angiosperms that complete their life cycle in 2 years • Perennials - flowering plants that live for more than 2 years

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