Biology Exam #2: Seedless Plants

Are there more Seeded or SeedLESS plants?

• Seeded plants

  • Reproduction by seeds

  • Vascular

  • Produce flowers

  • Seedless plants do NOT produce flowers

What adaptations have plants picked up to live on land?

• Challenge: obtaining H2O

  • Avoid dessication (dehydration)

  • Overcome gravity

  • Protection from ultraviolet radiation

  • Movement and protection of gametes

• Benefits:

  • abundant, unfiltered sunlight

  • CO2 is more readily available

  • no natural predators

• Early terrestrial plant life did not move far from aquatic environments at first

How do plants avoid desiccation?

• Staying close to aquatic environments

• tolerance to dry seasons developed over time

• colonization of humid habitats (ferns)

FOUR Major adaptations of terrestrial plants

1. Alternation of generations life cycle

2. Apical meristem tissue in roots and shoots

3. Waxy cuticle to prevent dessication

4. cell walls containing lignin

ALL OF THESE FEATURES ARE MISSING IN MOSS

Why do moss not have any of the 4 major adaptations?

• mosses were some of the first organisms that colonized the land

  • Intermediate species

Mosses

• Non-vascular

• seedless

• flowerless

• do not grow true roots or stems

• found in wet environments

  • require water for reproduction

Moss Anatomy

Sporophyte = Multicellular diploid form (the actual plant that you see)

• Capsule

• Spores

• Seta

Gametophyte= Multicellular haploid form, produces gametes by mitosis (Pollen in seed plants)

• Leaves

• rhizoids

Moss reproduction

Alternation of Generations

• All sexually reproducing organisms have both a haploid and diploid phase of their life cycle

• Haplontic life cycles: haploid state is dominate

• Diplontic life cycles: Diploid state is dominate

Sporangia in seedless plants

• Sporangia= Reproductive sac where spores are formed

• Homosporous= Produce one type of spore, gametophyte produces both male and female gametes

  • Non-vascular plants

• Heterosporous= Produce two types of spores, develop separately as male and female gametophytes, sporophyte is dominant

  • Some seedless and all seed plants

Apical meristem in Roots and shoots

• lengthen the plant with rapid cell division

• UNDIFFERENTIATED CELLS

  • Give rise to all specialized tissues

• Tips of roots and shoots (mitotically active)

Waxy cuticle

• Provides protection from water loss (Like chapstick)

• Prevents intake of carbon dioxide

  • Stomata or pores that open and close developed to regulate CO2 intake

Cell walls containing Lignin

• As terrestrial plants evolved competition for resources increased

  • Lignin helped in the ability to grow vertically in competition for sunlight

How do they protect themselves?

• Predation is unavoidable

• Terrestrial plants evolved both physical and chemical defense mechanisms

  • Thorns

  • Poisons

• some use fruits to attract animals to help spread seeds

• Chemicals

  • Humans have used chemicals in plants to create poisons and medications for thousands of years

The evolution of Land plants

• Ordovician period

  • Slow colonization of plants onto land

• Devonian period

  • Oldest known vascular plants

Major Divisions of Land plants

Land plants are divided into two main groups:

• seeded plants

  • vascular, reproduce by seeds, produce flowers

  • Seeded plants include angiosperms and gymnosperms

• seedless plants

  • non-vascular, do not produce flowers

  • seedless plants include mosses and ferns, which were among the first to colonize land.

Tracheophytes - Vascular plants

• 90% of Earths vegetation

• Have the ability to grow far away from H2O

  • Due to vascular tissue (xylem and phloem)

• Diploid sporophyte phase is dominant

• General Sherman Tree

  • SUPER TALl

What is vascular plant tissue?

tissue responsible for the transport of H2O and nutrients throughout the plant body

• Phloem

• Xylem

• Roots

Xylem

• Storage of H2O and nutrients

• Long distance transport of H2O and nutrients

• Transfer of H2O growth factors

• composed of rigid cells that help maintain plant structure

• UP-take of these nutrients

Phloem

• Transportation of sugars, proteins & other solutes throughout the plant

• Transports materials in both directions

Roots

• Not Well preserved in the fossil record

  • appear to have evolved after vascular tissue

• Anchor plants

• absorb H2O and nutrient from soil

leaves

• Increase photosynthetic ability of plants

  • More chloroplasts employed

  • increased surface area

• leaves evolved more than once

  • Microphylls

  • Megaphylls

• Sporophylls:

  • Leaves modified to bear sporangia (Pinecones, ferns)

Modern day seedless plants

• Fern

• Club moss

• horsetails

• whisk ferns

Why are seedless plant important?

• Recolonization of areas after distaster

• Provide food and shelter for organisms

• Provide info on the presence of pollution

• fix nitrogen in aquatic ecosystems

• Used by humans for food, meds and fuel

  • Dried peat moss burned for heat and fuel

  • Fossil fuel

Seeded vs. Seedless plants

Seeded plants reproduce by seeds, are vascular, and produce flowers. Seedless plants do not produce flowers and are non-vascular.

key points for NONvascular plants

• Have to get water and nutrients by direct contact

• limited growth potential due to lack of conductive tissues

• need water for reproduction

• alternation of generations

Key points for Vascular plants

• Have xylem/phloem

• Can grow far away from direct water sources

• can grow into large plants

• roots

• leaves