Lecture 1 Flashcards
What is systematics?
A science that proposes hypothesized ancestor-descendant relationships between organisms and classifies organisms into named groups based on relatedness
Uses both genetic and morphological/physiological evidence
What is the use of systematics to science and society?
Quantifying diversity: gives organisms names
Understand how groups are related: creates an ordered, hierarchical system, with different levels of classifications
List the classification hierarchy from largest group to most specific
Domain, kingdom, phylum, class, order, family, genus, species
Phylogeny
Hypothesized ancestor/descendent relationship, or evolutionary history, of a group of organisms
What is a clade?
A group of organisms made up of an ancestor and all of its descendants
What is a synapomorphy?
A trait and characteristic that is shared by members of a clade, implying that is was present in a common ancestor
What is homoplasy?
When the same trait arises in different lineages due to evolutionary pressure
Homoplacious traits (traits that are similar, but independently derived) can cause confusion in classifications
Describe monophyletic
A group that includes ALL of the descendants of a common ancestor–this group would satisfy the criteria to be a clade
Describe non-monophyletic
All other kinds of groups, these do not satisfy the criteria to be a clade.
They can be:
- Paraphyletic groups: a group that has all group members sharing a common ancestor, but does not include a small number of groups that are also descendants (e.g. dinosaurs do not include birds)
- Polyphyletic: a group that is made up of not-closely related smaller groups (i.e. not having a shared common ancestor) that have been erroneously grouped on the basis of homoplasious characters
What are algae/seaweeds?
Heterogenous group of aquatic photosynthetic organisms (that are not closely related to each other)
Many are multicellular, but do not share a multicellular ancestor
What are stramenopiles
Brown algae (includes multicellular keps)
Diatoms: unicellular, non-motile
Microalgae (plankton): either unicellular or in string
What are rhodophytes?
Red algae (includes multicellular nori)
Coral symbionts (unicellular)
What are viridiophytes?
Green plants/chloroplastida
Includes green algae and land plants
Monophyletic group
>300,00 described species
Traits that make them similar to each other and different from other groups (synapomorphies) are mainly chemical in nature
What are embryophytes and what are its the synapomorphies?
Land plants
- plants had to adapt to succeed out of water (the traits below are thought to have helped with this)
Traits:
- Embryo stage early in the life of the sporophyte (the sporophyte is the 2N life stage of plants)
- Multicellular sporophyte
- Multicellular reproductive structures
- A cuticle
What are the three types of bryophytes?
Mosses (quite diverse)
Liverworts (somewhat diverse)
Hornworts (not very diverse)
What are tracheophytes?
Vascular plants (spermatophyte dominant, vascular tissue more specialized)
- lycopods and similar
- ferns and relatives
- gymnosperms evolved seeds
- angiosperms evolved flowers and fruits
Describe mosses
Most diverse group of bryophytes
Upright, leafy gametophyte is dominant phase
Multicellular rhizoids
Stomates
No true roots
Can go dormant for a long time and can hold a lot of water
Describe the fertilization process of mosses
Gametophytes (haploid generation) are the main moss that we observe
- after an egg cell is fertilized by a male moss gametophyte sperm, the sporophyte (diploid) generation grows out of the top of female gametophytes (top right)
Capsule containing haploid spores breaks open (bottom right) and these go through a protonemal stage (like green algae filament), and then grow up into haploid male or female gametophytes
Describe liverworts
Approx. 9000 species, thalloid or leafy growth possible
Lack stomates
Gametophyte is the dominant phase
Same (or similar) reproductive cycle as mosses
Describe hornworts
Approx. 100 species
On chloroplast per cell
Meristematic growth of sporophyte similar to vascular plants
Describe main characteristics of tracheophytes (vascular plants)
Vascular tissue, xylem with tracheids (elongated cells, thickened cell wall, dead when functional)
Pits connect tracheids
Gametophyte dramatically reduced
Sporophyte very elaborate, branched
What are the three important groups of vascular plants?
Monilophytes: the seedless vascular plants which includes ferns and horsetails
Lycophytes: other spore-producing groups (such as clubmosses) with many extinct groups
Spermatophytes: seed plants, which includes the gymnosperms and angiosperms
What are some characteristics of early tracheophytes?
Multi-branced sporophyte
Tracheids
Reproduction via spores
Still no leaves or roots
Lycopodaceae
Spirally arranged microphyll (leaves with single veins)
Large sporangia with numerous spores, in leaf axils or in simple strobili
