Ch. 30 Plant Diversity II: The Evolution of Seed Plants

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Ch. 30 Plant Diversity II The Evolution of Seed
Plants
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The seed replaces the spore

• Spores used for first 100 million years of plant
  life on land
• A seed is a resistant structure that is
  multicellular and is more complex

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Overview

• Seed plants are vascular plants
• Produce seeds
• Three Important Reproductive adaptations
• Advent of seed
• Evolution of pollen
• Reduction of Gametophyte (produce gametes)

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Reduction of Gametophyte

• Alteration of generations
• 2N vs. 4N life stage
• Gametophyte haploid cell,
• Sporophyte dipliod cell

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Reproductive Adaptations

• Gametophytes of seedless vascular plants develop
  is soil independently
• Gametophytes of seed plants are protected in
  reproductive tissue of sporophyte generation

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Seeds for dispersing offspring

• Solution for resisting harsh climates
• Sporophyte embryo w/ food supply w/I protective
  coat
• Two types of sporangia produce 2 spores
• Megasporangia megaspores give rise to female
  gametophyte, kept w/ parent
• Integument cover megasporangium
• Microsporangia microspores give rise to male
  gametophyte
• Ovule integument, megasporangium, megaspore

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Pollen

• Microspore develop into pollen grain
• Pollination transfer of pollen to ovule

• Two Clades of seed plants (seeds/pollen)
• Gymnosperm
• Angiosperms

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Gymnosperms

• Means naked seeds
• Mesozoic era age of gymnosperm
• There are four divisions
• Cycad resemble palms
• Ginkgo fanlike leaves, gold and decidous in
  autumn
• Gnetophyta 3 genera not closely related
• Weltwitshcia, gnetum, gnetophyta
• Conifers

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Phylum Cycadophyta

• Resembles palms trees
• Cycads

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Phylum Ginkophyta

• Fanlike leaves, deciduous,

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Phylum Gnetophyta

• Three Genera
• Welwitschia giant strap like leaves
• Gnetum tropical trees, vines
• Ephedra a shrub of American deserts

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Conifers

• Cones Latin conus, cone and ferre, to carry
• Pines, firs, spruces, larches, most large trees
• Most are evergreen, retain leaves for year
• Needle shaped leaves, thick cuticles,
• Most pulp and paper come from conifers
• Largest and oldest organism on earth
• Largest phylum of plants

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Figure 30.8a Phylum Coniferophyta Douglas fir
Oregon Most used for timber
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Figure 30.8b Phylum Coniferophyta Sequoia
2500 metric tons 14 blue whales 40,000 people
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Figure 30.8bx Sequoias
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Figure 30.8c Phylum Coniferophyta Cypress
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Figure 30.8d Phylum Coniferophyta Pacific yew
Source of Taxol (treatment of ovarian cancer)
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Figure 30.8e Phylum Coniferophyta Common juniper
Fleshy sporophylls cones
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Figure 30.8f Phylum Coniferophyta A pine farm
Clones from cell culture produce seedlings
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Figure 30.8g Phylum Coniferophyta Wollemia pine
Thought to be extinct till found in 1994 40
individuals, in two small groves Living Fossil
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Life Cycle of Pine Step 1

• Pollen cones and Ovulate cones
• Pollen has microsporangia
• Meiosis
• Pollen grains
• Ovulate contains
• Scales each w/ 2 ovules
• Megasporangim
• Pollination
• Pollen falls on ovulate cones
• Drawn into ovule
• Pollen grain germinates forming pollen tube,
  digest its way through megasporangium
• Fertilization occurs 1 year after pollination

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Life Cycle Part 2

• Megaspore mother cell produces 4 megaspores, only
  one survives.
• Two archegonia develop each w/ egg
• Pollinization occurs

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Life Cycle Part 3

• New sporophyte has rudimentary
• Roots
• Embryonic leaves
• Food Supply (female gametophyte)
• Ovule developed into Pine seed
• Embryo (new sporphyte)
• Three Plant Generations
• One Gametophyte
• Two Sporophyte

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Figure 30.10 A closer look at pine cones (Pinus
sp.)
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Figure 30.10x1 Pine Sporangium with spores
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Pollen Grain
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Figure 30.10x3 Pine embryo
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Angiosperms Flowering Plants

• Most diverse and widespread
• Vascular seed plants producing a flower.
• Most diverse and widespread
• 250,000 known species (720 known gymnosperms)
• There are two classes of angiosperms
• Monocots- lillies, orchids, yuccas, palms, and
  grasses
• Dicots- roses, peas, buttercups, sunflowers,
  oaks, maples

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Refinements of Angiosperms

• Better xylem, better tracheids.
• Fiber cell for support of tracheids.
• Vessel Elements more efficient.
• Strong role in adaptations leading to flowers and
  fruits.

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Flowers reproductive organ

• Reproductive structure of angiosperm
• Flower specialized shoot w/ 4 modified leaves
• Sepals green, enclose flower before it opens
• Petals bright colors, Attractor, sterile,
  surrounds sporophyll (fertile)
• Stamen produce microspore, give rise to male
  gametophyte.
• Carpels female sporophyll, produces megaspore,
  give rise to female gametophyte

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Carpel Evolution Theory
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Fruit

• Mature Ovary
• Develops from Ovule
• Protects dormant seed
• Aids in dispersal
• Modifications (flower withers, fruit develops)
• Pericarp wall of ovary, thickened wall of fruit
• Pollination does not occur, no fruit develops

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Figure 30.16 Fruit adaptations that enhance seed
dispersal Red berries (left), dandelion (right)
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Figure 30.16x1 Dandelion seed dispersal
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Figure 30.16x2 A bird eating berries containing
seeds that will be dispersed later with the
animal's feces
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Fruit Classifications

• Fruits have several types
• Simple Fruit fruit from single ovary. Cherry,
  soybean pod
• Aggregate Fruit single flower that has several
  carpels. Blackberry.
• Multiple Fruit group of flowers clustered
  together. Walls of ovaries thicken and fuse
  together..become one fruit. Pineapple
• Inflorescence

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Life cycle of an angiosperm

• Pollen Grain
• Ovule
• Embryo Sac
• Cross pollination same species, different plant
• Stamen/Carpel mature at different time
• Arragment prevents self pollination
• Double Fertilization 2 sperm pollinate single
  ovule, triploid nucleus

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Figure 30.17 The life cycle of an angiosperm
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Figure 38.1 Simplified overview of angiosperm
life cycle
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Flowers

• Complete flowers have all four basic floral
  organs
• Incomplete flowers lacking one or more floral
  organs

• Bisexual Flower equipped with both stamen and
  carpel
• Trillium
• Unisex Flower missing either stamen or carpel

• Monoecious stamen and carpel are located on same
  individual plant
• Dioecious stamen and carpel located on separate
  plants

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Figure 38.4 The development of angiosperm
gametophytes (pollen and embryo sacs)
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Figure 38.7 Genetic basis of self-incompatibility
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Figure 38.9 Growth of the pollen tube and double
fertilization
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Figure 38.10 The development of a dicot plant
embryo
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Figure 38.11 Seed structure
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Coevolution

• Angiosperms and Animals have influenced each
  other.
• Mutual evolution b/w two species is CoEvolution
• Pollinator/Plant relationships
• Monkey and the Fig

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Figure 30.18 Flower-pollinator relationships
Scottish broom flower and honeybee (left),
hummingbird (top right), baobab tree and bat
(bottom right)
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Plants and Humans

• Agriculture based mostly on angiosperms
• Nonrenewable source
• Space for people vr. Plants
• Slash and Burn
• 50 million acres of tropical rain forest cut down
  per year (state of Washington)
• Source of medicine resource

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Figure 30.19 Deforestation is an international
practice
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Figure 30.19x Deforestation
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Table 30.2 A Sampling of Medicines Derived from
Plants