Lecture 2: The Tree of Life and Biodiversity [G] Flashcards
Wednesday 2nd October 2024
When did Darwin first sketch his tree of life?
In 1837
What was La Scala Nature?
- A view from the Medieval era (500-1500 AD) that was the hierarchal model of life arranged as the staircase to heaven.
- Example: Minerals → Fire → Plants → Animals → Humans → Angels → God.
- The higher the being is in the chain, the more attributes it has, including all the attributes of the beings below it.
How did Darwin come to his conclusion over the tree of life?
- Realised that fossils of animals no longer existed.
- Realised that there were the same number of organisms on earth
- Realised that some organisms disappeared and were subsequently replaced by other forms.
When did Darwin publish ‘On the origin of species’?
In 1859. This book first formalised the idea of natural selection driving evolution.
What happens to lineages over time?
They change and diverge
In Medieval times, what was used to show the hierarchy of organisms?
The Great Chain of Being
When did Linnaeus draw his tree of Classification?
In 1735
Who made the first attempt at systematic classification?
Linnaeus
How did Linnaeus’ tree of classification work?
He put the best species at the top, and organisms that we eat at the bottom. ( we were at the top)
Who introduced binomial nomenclature for systematic classification?
Linnaeus
Although Linnaeus did introduce binomial nomenclature for systematic classification, what was still wrong with his classification system?
Retained medieval biases (e.g., misclassification of whales as fish).
Which levels of classifiaction were used by Linnaeus?
Kingdom, Class, Order, Family, Genus, Species. (Modern taxonomy includes additional categories like domain and phylum, which Linnaeus did not have, but his work laid the groundwork for future developments in biological classification.)
Kings Play Chess on Fancy Gold Squares
Kingdom Phylum Class Order Family Genus Species
Was the medieval ‘march to progress’ correct or incorrect?
Incorrect
Describe Darwin’s insights from 1837
- Darwin conceptualized the idea that all living organisms are connected through a “Tree of Life.” nstead of viewing life as a hierarchical ladder (common in medieval thinking), he proposed that life forms diverged from common ancestors in a branching pattern. Each branch represented a lineage, and the points where branches split (nodes) represented shared ancestors.
- Recognized species extinction and replacement, but lacked knowledge of genetic mechanisms.
- In 1837, Darwin sketched his first evolutionary tree in his notebooks, marking it with the phrase “I think” at the top. This sketch demonstrated his realization that species are linked through shared ancestry and that this connection can be depicted as a tree with diverging branches.
- While Darwin understood the “what” of evolution — that species evolve and are connected through shared ancestry — he did not yet understand the “how.” At this time, the mechanisms of heredity and genetic variation were unknown. These would only be clarified later through Gregor Mendel’s work on inheritance and the eventual discovery of DNA.
What did Darwin do in the ‘Origin of Species’ 1859?
He first formalised the idea of natural selection driving evolution.
What eventually bridged the gap between Darwinian theory and modern genetics?
Gregor Mendel’s genetic experiments with peas
In 1937, who redefined evolution?
Theodosius Dobzhansky
When did Theodosius Dobzhansky redefine evolution?
In 1937
What did Theodosius Dobzhansky redefine evolution as in 1937?
‘a change in allele frequency in a gene pool’.
Is it true that Edward Hitchock used fossil evidence and branching diagrams (tree) to expand on Darwin’s findings?
Yes
Do mutations/variation cause divergence?
Yes. This is what Darwin predicted. He just did not have the experimental evidence to back this up.
What experiment was used in this experiment to investigate antibiotic resistance?
‘Bacteria exposed to increasing antibiotic concentrations evolved resistance in just 11 days. This showed that sucessive e mutations enable survival and adaptation under environmental pressures.’ Proved darwin’s idea that mutations can cause divergence.
How can linneages be examined?
- Behavioural and ecological studeies
- Molecular evidence (DNA, RNA, proteins)
- Morphological traits (both living and fossil species)
What evidence can be used to investigate the evolution of living and fossil whales?
- Morphological traits like how they feed, and teeth
- Molecular (the best evidence)
- Fossil records
Homologous Traits and Apomorphies
Key Definitions:
Homologous Traits: Derived from a common ancestor.
Apomorphy: A derived trait unique to a taxonomic group.
Synapomorphy: A shared derived character among multiple groups.
Homologous Traits and Apomorphies
Key Definitions:
Homologous Traits: Derived from a common ancestor.
Apomorphy: A derived trait unique to a taxonomic group.
Synapomorphy: A shared derived character among multiple groups.
What are Cetaceans?
Marine mammals that include whales, dolphins, and porpoises
How many suborders of whale are there?
2
How many years ago did the 2 suborders of whale diverge from each other?
34 million years ago
What are the 2 suborders of whale called?
- Mysticetes (baleen whales)
- Odontocetes (toothed whales)
Describe Mysticetes whales
- Baleen whales have baleen plates instead of teeth to filter food from the water.
- They are generally larger than toothed whales, and include the blue whale, humpback whale, and right whale.
Describe Odontocetes whales
Also known as toothed whales, they use teeth to hunt for prey, and include orcas, sperm whales, dolphins, and porpoises.