Chapter 25: Evolution of Life Flashcards
What is allopatric speciation?
Gene flow interrupted when a population is divided into geographically isolated subpopulations
What is an example of allopatric speciation?
The water in a lake may subside and form two lakes with separate populations
How many years ago was the Paleozoic
252 mya
What are the six periods the Paleozoic era is subdivided into?
- Cambrian
- Ordovician
- Silurian
- Devonian
- Carboniferous
- Permian
What happened during the Paleozoic era?
The colonization of land 500 mya.
What was the order of events of animals on land during the Paleozoic era?
First land animals (arthropods: insects) 420 mya
Then fish diversified (became dominant), then amphibians evolved from fish being the first vertebrates to colonize land.
How did the Paleozoic era end?
It ended with a large mass extinction which wiped out 90% of marine species, and 70% of terrestrial species.
How many years ago was the Mesozoic Era?
135mya
What is the Mesozoic era known for?
“Age of reptiles” including dinosaur fossils.
What happend during the Mesozoic era?
The supercontinent Pangea began to break apart leading to the formation of the atlantic ocean.
What happened during the Cambrian explosion?
Many animal phyla appear suddenly in fossils
Adaptations for predation
What was a key event during the Mesozoic era?
Evolution of dinosaurs, flying birds then extinction at the end of the Cretaceous period, due to large astroid.
How many years ago was the Cenozoic era?
95mya to the present
What happened during the Cenozoic era?
During the Cenozoic era mammals diversified and became the dominant land animals.
Modern animals primates (apes), whales, rodents in the paleogene and humans in the neogene.
What is sympatric speciation?
Speciation occurs in populations that live in the same geographic area.
which is less common sympatric or allopatric speciation?
Sympatric speciation is less common
Sympatric speciation occurs if gene flow is reduced by what factors?
- Polyploidy: gaining an extra chromosome
- Sexual selection
- Habitat differentiation
Hybrid zones reveal factors that cause what?
Reproductive isolation
What is a hybrid zone
A region where two different species mate and produce viable and fertile offspring (incomplete reproductive barrier).
What is an example of a hybrid zone?
Two toad species in the genus Bombina interbreed in a long narrow hybrid zone
What does Reinforcement mean in Hybrid zones?
Hybrids are less fit than the parent species.
Strong selection for prezygotic barriers reduces hybrid population
What is fusion in hybrid zones?
When reproductive barriers weaken, and the two parent species fuse into a single species.
What is an example of fusion?
Fusion of a sperm and egg during fertilization.
What is an example of reinforcement.
Brown colored turtles cannot blend in with white sand or tree so their easily eaten.
What is stability?
extensive gene flow from outside the hybrid zones overwhelms selection against hybrids, maintains prevalence of hybrids.
What is reproductive isolation?
The result of biological barriers preventing members of two species from interbreeding and producing viable fertile offspring.
Hybrids are the result of
Interspecific mating (mating between two species)
Reproductive isolation can be classified by wether factors are
before or after fertilization.
What are the Prezygotic barriers?
Habitat isolation
Temporal isolation
Behavioral isolation
Gametic isolation
Mechanical isolation
What is reduced hybrid viability?
Genes of different parent species impair the hybrids development or survival
What is an example of reduced hybrid viability?
Salamanders because their development doesn’t go to completion and if it does its feeble.
Reduced hybrid fertillity
Meiosis may fail to produce normal gametes, resulting in sterility, if the parent species have chromosomes of different number or structure.
What is an example of reduced hybrid fertility?
Male donkey + female Horse= Mule is robust (strong) sterile (infertile)
what is Hybrid breakdown?
First generation hybrids are viable and fertile, but offsprings of the next generation are feeble or sterile
What is an example of Hybrid break down
Hybrids between cultivated rice are vigorous and fertile but members of the next generation are feeble or sterile.
How has life on earth changed over time?
Groups of organisms arise, diversify, and fall over time
The geological record is divided into
Hadean, Archean, Proterozoic, and Phanerozoic eons.
The most recent eon is Phanerozoic
Paleozoic, mesozoic and cenozoic eras.
The known fossil record is biased in favor of species that
- existed for a long time
- were abundant and widespread
- had hard parts such as shells or skeletons.
On a 1- hour time scale animals originated about ____ minutes ago while humans appeared less than ___ seconds ago
Animals 9 minutes ago and humans appeared 0.2 seconds agp
Prokaryotes vs. Eukaryotes
Prokaryotes: single celled, no nucleus, no complex organells.
Eukaryotes: single or multicellular, has nucleus, has complex organells.
History of Life
Hadean: Solar system and earth
Archean: prokaryotes
Atmospheric oxygen
Single-celled eukaryotes
Multicellular eukaryotes
Animals
Colonization of land
Humans
Precursor for life on early earth
Earth formed 4.6 billion years ago
Collision of rocks and ice
Atmospheric oxygen, water vapor, released by volcanic eruptions and nitrogen and oxides
Meteorites (Murchinson) in which carried lips, simple sugars and nitrogenous bases.
Photosynthesis and the Oxygen revolution
O2 (produced by photosynthesis) reacted with iron and precipitated out into iron oxide sediments
O2 dissolved in water (oceans)
O2 began to gas out of oceans into atmosphere
O2 accumulated in the atmosphere.
What are the three consequences of oxygenation?
- oxygen can damange cells by attacking chemical bonds and inhibiting enzymes
- Prokaryotic groups became extinct.
- Survivors found refuge in anaerobic environments, others adapted to use O2
endosymbiosis
when a prokaryotic cell engulfs a small cell that would evolve into a mitochondrion
Serial endosymbiosis
Hypothesis that mitochondria evolved before plastids
Ediacaran biota eukaryotes include
soft bodied animals, algae
Cambrian explosion
Appearance of animal phyla 535-525 mya
