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Diversity Part 2: Plants
Chapter 23 Introduction to Plants
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Characteristics of Plants
Autotrophs Multicellular Eukaryotes Cell Wall is made out of Cellulose
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Photosynthesis Chemical Equation: CO2 + H2O C6H12O6 + O2
Word Equation: Carbon Dioxide + Water Glucose + Oxygen Sunlight Sunlight
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Common Ancestor The common ancestor of ALL plants is thought to be Green Algae In the early evolution of plants, they made the transition from aquatic to land environments
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But, decreased access to water as well…
Why Move onto Land? *Increased opportunity for photosynthesis* Increased access to sunlight Increased access to carbon dioxide Increased opportunity to reproduce and disperse (spread out) But, decreased access to water as well… How did plants overcome that barrier to successfully colonize on land??
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Importance of Mycorrhizae
Mycorrhizae is a mutualistic relationship between plants and fungi to help a plant absorb water and nutrients from the soil. This relationship helped plants transition to land.
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Cuticle Almost all plants have a cuticle covering their leaves and stems to prevent water loss The cuticle is waxy (lots of lipids) and holds water in The cuticle is also clear to let sunlight in for photosynthesis
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Reproduction & Dispersal
Once plants colonized land, certain adaptations allowed them to reproduce and disperse their offspring more effectively—this was the driving force for the evolution of plants
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Seedless vascular plants
Cladogram Angiosperms Flowering Plants Gymnosperms Evergreens Seedless vascular plants Ferns Bryophytes Mosses Evolution of specialized cells / tissue Evolution of cuticle Green algae
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Plant Groups Bryophytes (Seedless, Non-Vascular)-Mosses
Seedless, vascular plants- Ferns Gymnosperms- Evergreens (Pine Trees) Angiosperms-Flowering plants
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Mitosis is a type of cell division that makes an
exact copy of the original cell Can be Haploid to Haploid or Diploid to Diploid Meiosis is a type of cell division that makes cells with Half the number of chromosomes as the original cell Can only be Diploid to Haploid
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Plant Life Cycles: Alternation of Generations
An alternation between two distinct forms or generations that reproduce differently One generation is haploid and reproduces sexually The other generation is diploid and reproduces asexually
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Alternation of Generations
Multicellular diploid organism (2n) sporophyte mitosis meiosis Unicellular diploid zygote (2n) Unicellular haploid cells (n) (spores) fertilization Unicellular haploid gametes (n) mitosis Multicellular haploid organism (n) mitosis gametophyte
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Moss Life Cycle Moss Life Cycle
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Alternation of Generations
By definition, all plants alternate generations Gametophyte makes gametes n=haploid Sporophyte makes spores 2n=diploid
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Alternation of Generations Gametophyte and Sporophyte
Notice that the more advanced plants have a dominant Sporophyte The less advanced plants have a more dominant Gametophyte
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Seedless vascular plants
Cladogram Gymnosperms Angiosperms Seedless vascular plants Bryophytes Evolution of specialized cells / tissue Example: cuticle Green algae
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Non-Vascular Plants Bryophytes Example: Moss
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Bryophytes They are small and low to the ground because they do not have vascular tissue Found only in damp, moist areas on land 1) Leaves must absorb water for photosynthesis 2) Sperm swims through water to reach egg in gametophyte
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Bryophytes sporophyte gametophyte
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Seedless vascular plants
Cladogram Gymnosperms Angiosperms Seedless vascular plants Bryophytes Evolution of vascular tissue Evolution of specialized cells / tissue Evolution of cuticle Green algae
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Seedless Vascular Plants
Example: Ferns
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Key Adaptation over Nonvascular Plants
Vascular Tissue Set of tubes that transport materials around plant Allows plants to grow taller Water travels up through Xylem Sugar/Food travels throughout in Phloem
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Ferns Can Live Further Inland
Still must live in moist areas Sporophyte grows successfully with vascular tissue But sperm must still swim to egg in tiny gametophyte
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Fern Sporophyte
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Fern Gametophyte
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Fern Life Cycle Fern Life Cycle
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Seedless vascular plants
Cladogram Gymnosperms Angiosperms Seedless vascular plants Evolution of pollen grains / seeds Bryophytes Evolution of vascular tissue Evolution of specialized cells / tissue Evolution of cuticle Green algae
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Seed Plants Gymnosperms/Angiosperms Example: Pine Trees or Flowers
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Gymnosperms Examples: Spruce Tree, Fir Tree, Pine Tree
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Gymnosperms female ovary male pollen cone
Think cones (any conifer like pine trees) female ovary male pollen cone
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Pine tree Gymnosperms Sporophyte Dominates
tiny gametophyte inside cone sporophyte Sporophyte Dominates
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Gymnosperm Pollen Strategy
Release a lot, hope some pollinate (Meanwhile, irritating everyone else) Pollen is the male sperm in Gymnosperms and Angiosperms
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Key Adaptations Over Seedless Plants
Seeds Pollen Grains
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Seeds Tough coat protects newly fertilized embryo
Also contains supply of food (endosperm) to survive during dormancy period A seed in a gymnosperm is inside the cone
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Seed Dispersal Plants try to disperse offspring far away so they have a higher chance of survival. Dispersal of seeds prevents competition for water, nutrients, light, and living space.
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Seed Dispersal Dispersal by wind – wing-like structures, parachute-like structures
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Seed Dispersal Dispersal by animals – fruits have hooks that cling on animals fur, other fruits provide food for animals
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Seed Dispersal Seeds dispersal is completed by birds, small animals, wind, and water The tough, fibrous outer covering of a coconut provides protection as well as a floatation device
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Pollen Grain Hard covering around sperm, light weight allows travel by wind Removes water requirement for fertilization
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Pollen Grain Sperm At the very end when pollen lands on another plant of the same species Pollen tube connects to ovary, fertilizing egg
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Seedless vascular plants
Cladogram Gymnosperms Angiosperms Evolution of flowers / fruits Seedless vascular plants Evolution of pollen grains / seeds Bryophytes Evolution of vascular tissue Evolution of specialized cells / tissue Evolution of cuticle Green algae
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Angiosperms Think flowers Most diverse plant group
Most Dominant Plant group on the planet
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Key Adaptation Over Gymnosperms
Flowers Adapted for pollination by animals Attract animals to help carry pollen to the next flower Color or scent attractors guide animals to obtain sugar from plant Some angiosperms still wind pollinate (grass)
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Advertising in UV color
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Angiosperms are Divided into Monocots and Dicots
Monocots include: grasses, corn, rice, oats, wheat, orchids, lilies and palms Dicots include: shrubs, trees (except conifers) wild flowers and some garden flowers
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Monocots
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Dicots
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Monocot and Dicot Seed Structure
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Monocot and Dicot Leaf Veins
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Monocot and Dicot Flower Pedals
Monocot-pedals in groups of three or multiples of three Dicots-pedals in groups of 4s or 5s
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Flower Structure of an Angiosperm
Sepals protect the flower bud from insect damage and dryness The color, scent, and nectar of flowers attracts insects, bats, and birds These animals help to transfer the pollen from the anthers of one flower to the stigma of other flowers-called pollination
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Sunflower Angiosperms
tiny gametophyte inside bottom of flower rest of plant = sporophyte Sporophyte Dominates
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Pollen Tube Growth and Fertilization in Angiosperms
The Pollen grains are transferred to the Stigma where the pollen grain produces a Pollen tube The pollen tube grows down the style into the ovary where it fertilizes the ovule The fertilized ovule becomes a seed and the ovary develops into the fruit of the plant
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The Sporophyte is the dominant stage in the life cycle of the Angiosperms
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After fertilization, the ovary becomes the fruit and the ovule becomes the seed.
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Fruit Typically collects sugar to attract animals
Seeds survive animal digestive system, pooped out far away from parent (and with free fertilizer!) Some are not eaten by animals, just help wind carry seed Example: dandelion
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Seedless vascular plants
Cladogram Gymnosperms Angiosperms Evolution of flowers / fruits Seedless vascular plants Evolution of pollen grains / seeds Bryophytes Evolution of vascular tissue Evolution of specialized cells / tissue Evolution of cuticle Green algae
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Asexual Reproduction Plants can also reproduce asexually
Vegetative reproduction is faster than sexual reproduction. Vegetative reproduction is where many plant parts can grow to make a whole new organism when separated. Examples: Ivy or Potato
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Ginkgophyta or “Ginkgo Tree”
A division of seed plants that have only one living species The leaves of the plant are fan shaped The Ginkgo is the oldest tree in the world, once thought to be extinct Ginkgo’s are the lone survivor of a "family that existed more than 200 million years ago" and kept company with the dinosaurs
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Ginkgo Tree The male trees are preferred because female trees bear a fruit which, after dropping, emits a foul odor. The fruit is about the size of a cherry tomato Roasted nuts from Ginkgo biloba trees have long been considered a delicacy in their native China. Treatment for short-term memory loss is just one of many medicinal uses for the extract derived from the leaves of Ginkgo biloba trees.
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