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Chapter 8 - Plants Ms. Van Sciver’s Grade 7
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Plants Autotrophs – make their own food Multicellular Eukaryotes – have a nucleus Cells surrounded by cell walls.
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Plant Origins
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Land Adaptations Support Rigid cell walls Vascular tissue Reproduction
Gametophyte – Reproductive cells Sporophyte – Spores Zygote – fertilized egg Obtaining Water Non vascular – must contact water Vascular – tubes for water transport Retaining Water Cuticle Transporting Materials Non-vascular – diffusion/osmosis Vascular – tubelike tissue
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Plant Life Cycle
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Seedless Plants Non-Vascular - Bryophytes
Low Growing Materials transport from cell to cell Live in damp shady places Thin cell walls
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Bryophyte Life Cycle
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Non-Vascular - Mosses More than 10,000 species Gametophyte –
green- fuzzy appearing tiny leave like parts Root like structures – rhizoid Sporophyte stalk capsule contains spores
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Non-Vascular - Liverworts
More than 8,000 species Found – moist rocks along streams Gametophyte – “liver” shaped Sporophytes – too small to see in umbrella shaped stalk
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Non-Vascular - Hornworts
Fewer than 100 species Found in moist soil Sporophytes – slender, horn shaped
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Seedless Plants – Vascular
Ferns Horsetails Club Mosses True Vascular Tissue Release Spores Need water for reproduction
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Ferns More than 12,000 species True Roots, stems, leaves Sporophyte
Leaves – Fronds Spore cases Gametophytes Tiny Grow low to ground
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Fern Life Cycle
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Horsetails Few Species alive now Needle Like Branches Small leaves
grow in circle around joints Small leaves grow flat against stem Stem contains Silica
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Club Mosses Only a few hundred species Resembles branch of a pine tree
Ground pine Grows in spiral around stem
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Seed Plants Have Vascular Tissue Use Pollen and Seeds to reproduce
Xylem – carries water and minerals Phloem – carries food (sugars) Use Pollen and Seeds to reproduce Pollen – male reproductive cell Seeds – embryo, food supply, seed coat Gymnosperms Seeds not protected by fruit Angiosperms Produce Flowers Seeds protected by fruit
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Seed Structure Monocot – one cotyledon (seed leaf)
Dicot – 2 cotyledons
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Seed Dispersal Seeds must be dispersed to prevent competition
Water Sunlight Minerals Dispersed by Wind Animals
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Germination Needs- correct moisture, correct temperature, correct time – some seeds are dormant first
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Roots Tip Covered by a root cap Protects root during growth
New cells develop behind root cap Root hairs Tiny Absorb water, minerals Anchor plant in soil Xylem Phloem Fibrous Roots - spreading Taproot - deep
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Stems Xylem – carries mineral, water Phloem – carries food Supporting Cells Woody Stems Outer bark – Cork Living Phloem Cambium Living Xylem Sapwood Hardwood Annual Rings Herbaceous Soft No wood
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Leaves Conduct Photosynthesis Lose water from stomates during transpiration Guard cells control amount of water lost
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Gymnosperms Ginkgo Seed Not Protected by a fruit Needle like or scale like leaves Deep roots system Cycad tropical Conifer Largest group Cone bearing Gnetophyte Deserts, tropical rain forests Can live 1,000 yrs.
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Gymnosperm Reproduction
Pollination pollen - male parts Fertilization sperm reaches ovule Seed development Seed Dispersal
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Angiosperms Produce Flowers Seeds are protected by fruits Live almost
everywhere
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Flower Parts
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Angiosperm Life Cycle
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Dicots vs. Monocots
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Tropisms A plant grows toward a stimulus – positive A plant grows away from a stimulus – negative Touch – Thigmotropism Light – Phototropism Gravity – Gravitropism or Geotropism Hormones – Auxin – causes cells to lengthen on side away from light. Plant bends toward light.
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Seasonal Changes Photoperiodism – response to length of day vs. night.
Critical Night Length Short Day Plants – Bloom when daylight is shorter autumn Long Day plants – Bloom when daylight is longer – spring and summer Day Neutral – No effect
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Life Spans of Angiosperms
Annuals Complete cycle in one growing season herbaceous stems Biennials Year one – stems, leaves Year Two – flowers, fruits, seeds Perennials Flower every year Most have woody steam some have herbaceous stems leaves and stems die each winter, but new are produced in spring.
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