Taxonomy and Life Cycles Flashcards
Taxonomic Levels
- Domain
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
Plants are categorized by:
- Growth form: eg. herbs, shrubs, trees
- Life cycles: eg. annuals (yearly for growth), biennals (every two years for growth) and perennials (plants that persist for several years)
- Articles of diet: eg. fruits and vegetables
- Medicinal: eg. purgatives, doctrine of signatures
- Economic/Social: eg. crops, drug, shade etc.
- Reproductive features: eg. sexual, asexual
Taxonomy includes four aspects…
- Description
- Identification (assignment of features)
- Nomenclature (naming the organism)
- Classification (placing organisms into definite categories)
Nomenclature
- Genus name (starts with upper case letter)
- Species name (starts with lower case letter)
When hand-written each name is underlined with ITS OWN separate SINGLE, STRAIGHT line
Phylogeny
- Refers to the evolutionary history and relationships among species or groups of organisms.
- It illustrates how species have evolved from common ancestors.
Cladistics
A method of classifying organisms based on common ancestry, emphasizing the branching order of the evolutionary tree without considering the degree of difference.
Only emphasizes shared characteristics
Systematics
A broader field that encompasses both taxonomy and phylogenetics.
The Three-Domain Model
- Made by Carl Woese and George Fox
- Made in 1999
- Made to rearrange and classify life
- Includes: Eukaryota, Bacteria and Archaea or Eukarya, Eubacteria and Archaea
Eukarya
consists of unicellular to complex multicellular organisms. ALL with eukaryotic cells
Archaea
also prokaryotes, most often encountered as extremophiles that are poisoned by oxygen
Eubacteria
comprises all typical bacteria, the more well known of prokaryotes.
Asexual Reproduction in Algae- Mitosis
- Some unicellular forms of algae (eg. Euglena) reproduce by mitosis (eukaryotic fission)
- The parent cell divides (longitudinally or transversely) into two similar parts
Asexual Reproduction in Algae- Fragmentation
Eg. Ulva, Sargassum
- The parent body breaks up into two or more fragments that grow into new organisms.
Asexual Reproduction in Algae- Sporulation
Eg. Chlamydomonas, Chlorella and Ulothrix
- Formation of spores in normal vegetative cells or specialized cells known as sporangia. The spores swim away (zoospores) from the parent, settle down and develop directly into new filaments.
Asexual Reproduction in Algae- Autocolony Formation
Eg. Volvox sp.
- Daughter colonies form within the parent colony.
- New daughter colonies form from certain cells (initials) in the surface of the colony.
-Eventually, the parent colony will rupture and release the mature daughter colonies.
Sexual Reproduction Cycles
a) Zygotic Meiosis- meiosis in the zygote (the only 2n in the cycle)- mainly in freshwater Chlorophyta.
b) Gametic meiosis- for the production of gametes- mainly in marine Chlorophyta and Phaeophyta.
c) Sporic meiosis- for the production of spores, involves an alternation of generations (sporophyte to gametophyte and back to sporophyte)- in marine Chlorophyta, Phaeophyta and Rhodophyta.
Zygotic Meiosis
- A mature, dominant adult organism is a haploid individual which produces gametes by mitosis. (Eg. Fungi)
- These haploid gametes combine to form a diploid zygote
- Zygote immediately divides by meiosis to form 4 haploid cells
- The zygote may develop into a zygospore to ‘ride out’ unfavorable environmental conditions, then divide into the haploid cells when normal conditions return
Zygotic Meiosis-Conjugation
This happens in some freshwater green algae, eg. Spirogyra.
Steps:
- Two normally vegetative cells in adjacent filaments of Spirogyra suddenly behave as gametes
- Fuse via a conjugation tube
- Form a zygote
- Meiosis to form four new (haploid) cells
- Grow into new Spirogyra filaments
Gametic Meiosis
- A mature, dominant adult is a diploid individual (Eg. Acetabularia)
- Diploid individual undergo meiosis giving haploid gametes
- Each pair of haploid gametes combine to form a diploid zygote
- Zygote develops into the diploid individual
Since gametes are produced by meiosis —-> gametic meiosis
Sporic Meiosis
- Mature adult may exist either as a haploid gametophyte or as a diploid sporophyte
- The gametophyte produces the gametes (2 haploid)
- These gametes will then fuse to form the diploid zygote
- The zygote will then divide to produce a sporophyte
- The sporophyte produces haploid spores within sporogenous tissue via meiosis
- The spores will then develop via mitosis into multicellular haploid individuals (new gametophytes)
Isomorphic alternation of generations (Sporic meiosis)
In many marine green algae that reproduce via sporic meiosis, the sporophyte and gametophyte individuals appear the same externally.
Eg: Chlorophyta, Ulva
Heteromorphic alternation of generations (Sporic meiosis)
The sporophyte and gametophyte individuals appear quite different externally.
Eg: Derbesia and Bryopsis
