Exam 3 Flashcards
Taxonomy
science of classifying organisms into taxa with a traditional Linnaean system (after Carl Linnaeus) uses a nested hierarchical system
At each sublevel in the taxonomic classification system, organisms become more similar.
Binomial nomenclature
Species name = genus + species ‘epithet’
Biologists group organisms based on shared characteristics. What are the 6 traits?
Fossil records
Morphology
Physiology
Behavior
Embryological development
DNA/RNA sequences
Phylogenetic systematics
Reconstruction and study of evolutionary relationships
Phylogeny
Hypothesis about relationships among taxa
Depicted as a phylogenetic tree or cladogram
A branching diagram depicting evolutionary relationships
Taxon (taxa, pl)
group(s) of organisms (species, family, domain, etc.)
Clade
any branch or lineage (lines in cladogram)
Branch point (node)
splitting represents single lineage evolving into two clades
Nodes are most recent common ancestor (MRCA) of subsequent clades
Limitations of cladograms
Often, closely related taxa look similar, but not always
If evolved under different circumstances (selection pressures), the taxa may look very different despite their close relation
Unless specified, the length of the clade does not indicate amount of time passed since divergence (node)
Two Options for Similarities
Homologous characters
Analogous characters
Analogous characters
Similar due to functional or ecological constraints/pressures
Characters can be very similar in appearance due to convergent evolution
Convergence occurs in unrelated (or distantly-related) taxa when characters are shaped by similar ecological or evolutionary constraints (selection pressures)
May be referred to as ‘homoplasy’ (instead of homology)
Homologous characters
Similar due to divergent evolution (same ancestral source)
Based on genetics and developmental origin
The deeper the similarity, the more likely it’s of same origin
Monophyletic groups (monophyly)
the most recent common ancestor and all descendants
According to cladistic analysis, only monophyletic groups should be named and recognized
Building Phylogenetic Trees
All organisms within a clade share an exclusive point (node) on the tree.
A clade may contain multiple groups, as in the case of animals, fungi and plants, or a single group, as in the case of flagellates.
Groups that diverge at a different branch point, or that do not include all groups in a single branch point, are not considered true clades.
Ancestral character state (aka plesiomorphy)
The character state present in a lineage immediately before a character state change
Found in common ancestor of taxa, but not all displayed taxa have it
Basal clade taxon is expected to display most ancestral character states
Shared derived character state (aka synapomorphy)
Arose (derived) within the larger clade
Distinguishes taxa that share it from those that do not
Provides information about relatedness within the larger group
Used to identify branch points (nodes) within the larger clade
Rule of parsimony
Prefer the simplest cladogram with the fewest steps or events
Two patterns of evolution that may be misleading
Convergent evolution
Evolutionary reversal
Convergent evolution
Structures evolving from same evolutionary pressures but not from a common ancestral trait
Example: wings in birds and wings in insects
Example: leglessness in (some) lizards and leglessness in snakes
Evolutionary reversal
Ancestral traits are sometimes lost in descendants in one group
Example: loss of limbs in snakes (most other squamates have legs)
Example: loss of hindlimbs in cetaceans
6 reasons why do phylogenies matter?
- Understanding of evolutionary processes
- Research on related species may help to better understand human health, medical issues
- Track evolution of parasites and viruses
- Use biotechnology to produce more productive crops, domesticated animals
- Produce more effective drugs (e.g. human insulin)
- Improve conservation efforts for threatened and endangered species
Organismal Ecology
Study of adaptations that enable individuals to live in specific habitats. These adaptations can be morphological, physiological, and behavioral.
Population Ecology
Study of demography and intraspecific interactions; includes the number of individuals in an area and how and why population size changes.
Community Ecology
Study of interspecific interactions at small and large scales (e.g., symbiosis and succession, respectively
Ecosystem Ecology
Study of the storage and movement of nutrients and energy among organisms and the surrounding atmosphere, soil, and water.
Landscape Ecology
Study of biomes and the conditions that influence their dispersion.
Biogeography
the study of the geographic distribution of living things and the abiotic factors that affect their distribution.
endemic species
one which is naturally found only in a specific geographic area that is usually restricted in size.
cosmopolitan species
species which live in a wide variety of geographic areas.
Abiotic Factors affecting distribution
Energy Sources
Sunlight
Ocean Upwelling
Temperature
Presence, Type, and Changes in Water
Freshwater
Saltwater
Frozen water
Seasonal water changes
Nutrients and Inorganic Materials
Other factors:
Aquatic: Oxygen, salinity, currents, tides, vents
Terrestrial: Fire, wind
Both: Volcanism, tectonics, natural events
Ocean upwelling
an important process that recycles nutrients and energy in the ocean. As wind pushes offshore, it causes water from the ocean bottom to move to the surface, bringing up nutrients from the ocean depths.
Fire impact
mature cones of the jack pine (Pinus banksiana) open only when exposed to high temperatures, such as during a forest fire. A fire is likely to kill most vegetation, so a seedling that germinates after a fire is more likely to receive ample sunlight than one that germinates under normal conditions
Using your understanding of ocean upwelling, explain one reason why marine life is more abundant near some coastlines than others.
Draw and label a cladogram depicting the relationships of four taxa (A, B, C, and D). Taxon A occupies the basal clade. Taxa B and C are sister taxa. Indicate the occurrence of a homologous characteristic shared by all taxa (refer to it as ‘cells’). Then indicate the occurrence of an analogous characteristic shared by taxa C and D (refer to it as ‘aerobic’).
Use the cladogram below to complete the following:
What named group is monophyletic?
What ancestor is shared by all displayed taxa?
What shared derived character is diagnostic of bilateria?
bilateral symmetry
ancestor 1
having bilaterial symmetry
Climate
long-term, predictable atmospheric conditions of a specific area
Weather
conditions of the atmosphere during a short period of time
A specific weather event occurring in a particular region is not evidence of global climate change
Different biomes
Tropical forest
Desert
Tundra
Temperate forest
Boreal forest – taiga
Temperate grassland
Savanna (grasses)
Chapparal – scrub forest
Aquatic zones in water
Neritic zone (shallow coastline)
Intertidal Zone
Photic Zone
Aphotic zone
Abyssal zone
Benthic realm
If you were to travel up Mount Kilimanjaro in Tanzania, you would pass through several habitats: savanna at the base, forest on the slopes, and tundra near the top. Explain how such diverse habitats can be found at one location near the equator.
