Chapter 8 - Plants Ms. Van Sciver’s Grade 7

Plants Autotrophs – make their own food Multicellular Eukaryotes – have a nucleus Cells surrounded by cell walls.

Plant Origins

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

Plant Life Cycle

Seedless Plants Non-Vascular - Bryophytes Low Growing Materials transport from cell to cell Live in damp shady places Thin cell walls

Bryophyte Life Cycle

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

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

Non-Vascular - Hornworts Fewer than 100 species Found in moist soil Sporophytes – slender, horn shaped

Seedless Plants – Vascular Ferns Horsetails Club Mosses True Vascular Tissue Release Spores Need water for reproduction

Ferns More than 12,000 species True Roots, stems, leaves Sporophyte Leaves – Fronds Spore cases Gametophytes Tiny Grow low to ground

Fern Life Cycle

Horsetails Few Species alive now Needle Like Branches Small leaves grow in circle around joints Small leaves grow flat against stem Stem contains Silica

Club Mosses Only a few hundred species Resembles branch of a pine tree Ground pine Grows in spiral around stem

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

Seed Structure Monocot – one cotyledon (seed leaf) Dicot – 2 cotyledons

Seed Dispersal Seeds must be dispersed to prevent competition Water Sunlight Minerals Dispersed by Wind Animals

Germination Needs- correct moisture, correct temperature, correct time – some seeds are dormant first

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

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

Leaves Conduct Photosynthesis Lose water from stomates during transpiration Guard cells control amount of water lost

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.

Gymnosperm Reproduction Pollination pollen - male parts Fertilization sperm reaches ovule Seed development Seed Dispersal

Angiosperms Produce Flowers Seeds are protected by fruits Live almost everywhere

Flower Parts

Angiosperm Life Cycle

Dicots vs. Monocots

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.

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

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.