Midterm 1 Flashcards
Lamarck’s Evolutionary View (not done)
- Inheritance of acquired characteristics
- Use and disuse. Body parts used are more developed and parts not used deteriorate.
- Reject because implies ……
LUCA
“The last universal common ancestor”. The hypothesized common ancestral cell from which Bacteria, Archaea, and Eukarya all originated.
Homologous Structures
Organs or skeletal elements found in different organisms that suggest a common ancestor. E.g. the arm (from clavicle to phalanges) in humans, seals, and bats.
Analogous Structures
Structures in species with similar function but that developed independently and are not from the same evolutionary origin. E.g. Insect and bat wings.
Vestigial Structures
Structures that seem to have lost their original functions in the species over an evolutionary timescale but still remain. E.g. the tailbone in humans.
Transitional Species
An organism that exhibits traits common to both an ancestral group and its derived descendant group. E.g. Tiktaalik showing the transition of vertebrate life from water to land.
Microevolution (not done)
Changes in allele frequency that can be observed within a population. 3 mechanisms:
- Mutations:
- Gene flow: the transfer of alleles (variants of a gene) from one population to another. Gene flow occurs when individuals or their gametes are able to migrate between populations that are physically separated.
- Genetic drift:
The Bottleneck Effect
The Founder Effect
Speciation (3 Types)
The splitting of an ancestral population into two species.
- Allopatric: two populations that through some process is split in two physically and become unable to maintain gene flow. E.g. the Butterfly fish becomes Lined BF and Reef BF.
- Parapatric: populations spread over a long environmental gradient and they start separating to specialize for their environment. E.g. polar and grizzly bears (though not yet fully).
- Sympatric: a population that’s dispersed and there’s a pocket of individuals that become their own species. Speciation within the species. E.g Hawthorn flies laid eggs only on hawthorn fruit, but some decided to lay eggs on apples instead and those became a different species.
As species undergo their own mutations, natural selection and genetic drift they may become reproductively isolated from each other.
Hadean Eon
- 4.6 to 4 billion years ago
- Intense volcanic activity, high temperatures, frequent asteroid impacts, and formation of the first oceans
- Heavy elements sink to core, light elements stay at crust
- Possible RNA synthesis because of reducing atmosphere (O2 lacking, H2 and CO present)
Archean Eon
- 4 to 2.5 billion years ago
- First evidence of rock formations
- High heat flow, but cooling off stage causing slowing of tectonic plates.
- Earth’s magnetic field weak/unstable due to limited UV
- Life originated (boundary of Hadean and Archean) through abiogenesis.
- 3.5 billion years ago first identifiable fossils (stromatolites)
- 2.7 billion years ago The Great Oxidation Event. Stromatolites cause O2 release and binds with iron. Iron dissolved out of oceans and O2 started to off gas into atmosphere.
Proterozoic
Paleozoic
- Why is the theory of evolution well accepted?
It’s supported by various independent lines of evidence: direct observation, homologous/vestigial structures, the fossil record, and biogeography
In which eon did LUCA first appear?
The last universal common ancestor first appeared in the Archean eon due to abiogenesis. It needed a habitable planet, a reducing atmosphere, RNA, and protocells.
Endosymbiotic Theory
The endosymbiotic theory proposes that eukaryotic cells originated through a symbiotic relationship between primitive prokaryotic cells. It suggests that mitochondria and chloroplasts were once free-living bacteria that were engulfed by a larger host cell, eventually evolving into organelles. This theory is supported by evidence such as their own DNA, double membranes, and similarities to bacteria in size and reproduction.
Abiogenesis
The process by which life originated from non-living chemical substances on early Earth, leading to the formation of simple organic molecules and eventually self-replicating systems. Requires habitable planet, reducing atmosphere (absence of O2), self-replicating machinery like RNA, and self-assembling machinery like protocells.
When did the earliest eukaryote fossils appear?
3.5 billion years ago in the Archean eon (stromatolites)
The Great Oxidation Event
2.7 billion years ago in the Archean eon. Stromatolites caused O2 release, which bound to the the iron in the oceans. Iron dissolved out, but O2 was still being released and eventually off gassing. 1-10% of current atmospheric oxygen.
When did eukaryotic cells arise?
2 billion years ago (Proterozoic eon) through endosymbiosis:
1. Evagination of cellular membrane
2. Formation of nucleus due to evagination
3. Gram bacteria engulfed
4. Host and endosymbiont become one organism
Darwinian Evolution
Descent with modification explains how species change over generations, inheriting traits from their ancestors while gradually accumulating differences. 1. Individuals with better suited traits for an environment are more likely to leave offspring.
2. If the traits are hereditary they will become more dominant in future populations
3. What was once better suited may not always be.
4. If an adaptation leads to reproductive isolation, it will create a new species.
Age of the Dinosaurs
The Mesozoic eon
Types of speciation
Allopatric: two populations geographically separating preventing gene flow
Parapatric: population spread over a strong environmental gradient that specialize for their needs
Sympatric: speciation within species
