Download Chapter 20 Multi cellular Algae Kingdom Plantae

Chapter 20 – Multi-cellular Algae
Kingdom Plantae
• All multi-cellular, autotrophic organisms with cell walls
Problem – Many scientists still classify multi-cellular algae with protists rather than
with plants.
Similarities between multicellular algae and plants:
•
Both are autotrophic.
•
Both are photosynthetic.
•
Both have cell walls.
•
Both have alteration of generation. (definition to come)
Differences between multicellular algae and plants:
• Algae have no internal transport system – plants do.
• Algae have no roots, leaves, or stems – plants do.
• Algae have some single celled examples – plants do not.
As a result, there are a few single celled examples of algae, but for the most part,
algae are considered to be part of the Plantae kingdom.
Multi-cellular Algae
• Contains chlorophyll A and one of the several other chlorophylls.
• Reproduce sexually with alternation of generation.
o Alternation of Generation: a life cycle that switches between haploid
(N) cells or organisms and diploid (2N) cells or organisms.
in other words, part of the life cycle has haploid structures and
part of the life cycle has diploid structures.
• Often no more than 2 or 3 cells thick.
• May or may not have accessory pigments to absorb different wavelengths of
light.
o Aiding photosynthesis.
Ex) Red light is absorbed more in shallower waters and blue
light is absorbed more in deeper waters.
3 Phyla of Algae
~Groups are divided based on the type of chlorophyll, accessory pigments, and the
form in which food is stored.
1) Phylum Chlorophyta
• Have chlorophyll A & B
• Known as green algae
• Store food as starches
• Fresh and marine water
• Can be single celled, colonial, or multicellular
• Have cellulose in their cell walls.
• May be the evolutionary link to land plants (mosses.)
Examples – 3 types to know
A) Single celled
Example: Chlamydomonas
• Fresh water organisms
• Egg shaped with 3 flagella
• Have an eyespot
• Have a cell wall without cellulose
• Can be put in Kingdom Protista but they do share more in common
with plants because they reproduce with alternation or generation.
Page 437 copy the Chlamydomonas
Reproduction of Chlamydomonas:
Life cycle:
• Most of its life cycle is in the haploid stage
• As long as conditions are good, it will reproduce asexually by mitosis.
• Each division produces zoospores – a haploid asexually produced cell.
• When conditions turns harsh or unfavorable …
Sexual reproduction:
• 2 cells, gametes (N) from different parent cells, come together.
• Because they look the same we call them isogamy :
iso = same, gamy = sex cell.
• The gametes fuse together in a process called syngamy and produce a
zygote (2N)
• The zygote produces a thick protective wall.
• When conditions are good again mitosis occurs and haploid cells are
released.
Page 440 Copy the life cycle.
B) Colonial – many identical living together that can still function independently.
• Do not form specialized tissue
Example: Volvox (page 438)
• 500-500 000 cells
• form a sphere
• all cells identical ( some cells are specialized for reproduction.)
Example; Spirogyra & Oedogonium
• Filament colonies
• Long chains of cells
• At one end is a specialized cell called the holdfast cell used to anchor
the colony
• Have specialized cells for reproduction
C) Multicellular
Example: Ulva
• Marine water on rocky sea coast.
• Called sea lettuce because they look leafy.
• Only 2 cells thick.
• Have holdfast cells.
Reproduction – Alternation of generation
~ Sporophyte – diploid plant
~ Gametophyte – haploid plant
• Gametes do not look the same - Heterogamy
Sexual reproduction:
• 2 gametes (N) meet and fuse together (syngamy) to produce a diploid
zygote (2N)
• The zygote grows into a multi-cellular sporophyte
• Specialized cells divide by meiosis to produce haploid zoospores (N)
• The zoospores grow into multi-cellular gametophytes, which produce
gametes.
• The multi-cellular sporophyte and gametophyte look the same.
Page 441 Copy the life cycle
2) Phylum Phaeophyta
• Known as brown algae
• Has chlorophyll A & C
• Have brown accessory pigments
• Stores food as special starches and oils
• Marine water
• Most common seaweeds are brown algae
• The largest brown algae can grow up to 60m Long (kelp)
• Brown algae have air bladders to help keep them upright.
• Have holdfast cells to attach them to the ground.
Example: Fucus
Reproduction – Alternation of generation
• Heterogamy; one gamete is larger/non motile; the other is smaller, has a
flagella and can swim.
• Gametophyte stays single cellular
• Sporophyte is multi-cellular
• On the blade of the Fucus are special areas that produce eggs and sperm
• The sperm swim to the egg > fertilization
• New sporophyte grows!
3) Phylum Rodophyta:
• Known as red Algae
• have chlorophyll A & D
• have red accessory pigments
• store foods as special starches
• found in deeper marine water
• more blue light is absorbed
Example: Porphyra – dried and used in sushi
Importance of Algae
• Phytoplankton (food)
• Provides habitats for aquatic environments
• Produces much of all the Earths oxygen
• Contains some chemicals that aid in some health problems
o Examples:
- Ulcers
- High blood pressure
• Used in foods – toothpaste, ice cream,
• Used in plastics, waxes, and paints