Broad Patterns of Evolution Flashcards
Order of Geological Periods
1) Cambrian
2) Ordovician
3) Silurian
4) Devonian
5) Carboniferous
6) Permian
Ancestors of Modern Mammals
- cynodonts
- synapsids
- therapsids
At what time was most of the landmass of Earth consolidated into one supercontinent?
from 1 billion years ago to about 250 million year ago
What is scenarios from which an adaptive radiation might directly arise?
- vacant ecological niches
- evolutionary innovation
- an adaptive radiation in a group of organisms (ex. plants) that another group uses as food
- colonization of an isolated region that contains suitable habitat and few competitor species
Example of Adaptive Evolution
the more than 500 species of fruit fly on the various Hawaiian Islands (all descended from a single ancestral species)
Striking Adaptive Radiations
- have occurred over limited geographic areas
- can be initiated when a few organisms make their way to a new (often distant location) in which they face relatively little competition from other organisms
- occurs within a single lineage
Plate Tectonics
is the theory that the continents are part of great plates of Earth’s crust that essentially float on the underlying portion of the mantle
Biogeography
is the scientific study of the past and present geographic distributions of species
Exaptations
are structures that evolve in one context but become co-opted for other functions
Evolutionary Trend
is a pattern of succession toward a particular characteristic in a group of related organisms
Condition of Permian (oceanic & atmospheric)
- anaerobic bacteria could thrive in reduced oxygen environments and emitted H2S (poisonous metabolic by-product)
- higher global temperatures caused a drop in oxygen concentrations by reducing temperature difference between the poles and equator and slowing the mixing of ocean water
- reduced ocean oxygen is associated with the Permian mass extinction
The Permian Mass Extinction (between Paleozoic & Mesozoic Era)
caused by extreme volcanism (which produced multiple environmental effects)
Evidence suggests that life originated in which eon?
archaean
Examples of adaptive radiation in organisms
- honeycreeper songbirds of the Hawaiian Islands
- Anolis lizards of the Caribbean
- Horses and deer in the post-dinosaur age
Convergent Evolution
occurs when selective pressures produced by similar conditions favor the evolution of similar solutions
Ex. of similar conditions (habitat)
Anolis Lizard ecomorph has long legs
- trunk/ground
- need long legs to jump from one brand perch to another
How was the genetic relatedness of ectomorphs determined?
by comparing their mitochondrial DNA sequences
The Evolution of Anolis Lizard in the Caribbean
the phylogeny of ectomorphs on a given island reveals that adaptive radiation has taken place
What is the main selective pressure behind the evolution of different Anolis lizards species in the Caribbean?
specific ecological niches
Different species evolve in response to
selective pressures created by specific ecological niches on the islands
The evolution of different ectomorphs was what time of selection?
- example of disruptive selection
- each new ectomorph had characteristics that were ideal for a particular habitat
- these characteristics developed causing the lizards to lose the ability to survive effectively in the other habitats on the island
How did some stickleback populations come to live exclusively in fresh water?
- some stickleback populations became trapped in lakes that formed at the end of the last ice age
- populations established when marine populations became trapped in the freshwater lakes where they migrated to spawn annually
- these lakes (formally connected to the ocean) were cut of by retreating ice fields
What do different environments provide?
can provide different selective pressures on an organism’s morphology
Why do some stickleback populations lack pelvic spines?
- in lakes with dragonfly larvae (pelvic spines can be a disadvantage) allowing the predatory larvae to grab the fish
- in lakes where there are no large predatory fish (there is no advantage to having pelvic spines)
Geneticists
use crosses to map the location of genes
Regulatory Regions
- presence of mutations that affect regulation of gene expression
- the gene remains intact but the location of its expression changes
- conveying a new phenotype without losing existing capabilities
Line of Evidence in Stickleback Evolution
Genetic Evidence - reveals the precise molecular mechanism responsible for the change in the pelvic structures
Fossil Data - show a pattern of evolution over long stretches of time
Data - obtained by analyzing living fish in lakes show the selective pressures present in different environments
Morphological Changes - occur in the fossil record as in living populations (might deduce that the genetic mechanism discovered in the living populations might be responsible for the changes observed in fossils)
Evolution
- repeats itself
