Theme 3 Flashcards
How many extant species have been described?
1.7 million
This is only 1/5 of the estimated total number of species.
For every extant species, how many have gone extinct?
Approximately 100
This highlights the ongoing process of extinction in nature.
How many extant and/or extinct species have existed since the beginning of life?
850 million
This figure encompasses both current and past species.
What does biological diversity reflect?
An interaction between preceding forms and ongoing processes of change
What is the nature of all species?
All species are temporary
Extinction is a natural part of the life cycle of species.
What process explains biological diversity?
Evolution
How did Darwin define evolution?
‘Evolution’ as descent with modification.
This definition highlights the idea of change over generations.
What results from changes in populations over time?
Evolution.
This reflects the dynamic nature of species and their adaptations.
What is the working definition of evolution in BIOL 243?
Change in allele frequency in a population over time.
This definition focuses on genetic variation within populations.
Darwin Background
- Wealthy, dad was doctor
- Failed Med school, didn’t like blood
- Could only study natural world via religious organizations, but failed to become priest
- Got opportunity to be captain companion on Beagle Boat to give company + religious advice (More info other slide)
Voyage of the Beagle
- 5 years long
- On ports, Darwin got off boat because he got sea sick and took notes + samples across coast to England
- Sent ~1500 samples back (fossils, plants, etc)
- Galapagos had a strong impact on Darwin
What concept explains that some species survive while others go extinct?
Curier’s idea of extinction
Curier noted the existence of fossilized bones from species that no longer exist.
Showed lare bones in USA belonged to extinct mastodon, not Elephants
Who proposed that the Earth must be much older than previously believed?
Lyell
“Principle of Geology”
- Proposed by Lyell
- Landforms developed/changed gradually through geological processes (not catastrophes)
Jean-Baptiste Lamarck ideas
- Transmutation - Species changed over time
- Lamarckism - Acquired traits can be inherited, lost through disuse
- Made Darwin think of imheritance
- Mechanism of acquired traits was dismissed
Thomas Malthus Ideas
- Principle of Populations - Human pops can increase faster than food supply, leading to competition for survival
- Those better suited (fittest) will survive
- Graph, y-axis qunatity, x is time. Food resources linear increase, pop jumps*
Darwin Post-Voyage
- Organized samples & books
- Spent 20 years examining evidence, wanted theory to be as solid as possible
Early Ideas on Selection
- Artificial selection well understood in dogs, crops, livestock, etc
- If humans can do so, why can’t nature?
Darwin’s Finches
- Convinced Darwin of evolution
- Small beaks for bugs, big strong for nuts
- Those from closer islands were more similar
*
Alfred Russel Wallace
- Had nat sel idea independently of Darwin but later in 1858
- Spurred Darwin to publish
Origin of Species + Nat sel
- November 1859
- Nat sel is triangle, pop has variation –> some variation has better reproductive success –> if heritable, variation is inherited –> inherited variation becomes fixed and species get more distinct
- From struggle of existence via limited resources = favourable variation preserved, unfavourable destroyed
How can Nat Sel occur?
- There’s variation in a trait
- Trait is heritable
- Some variants survive and reproduce more than others
Parts of environment can generate nat sel on a trait
Life Associated with Environment
- Adaptations made based on environment
- I.e. Stickbug, anglar fish light
Galapagos Islands Notes
- Terrestrial species don’t ghave many relatives nearby
- Neighbouring islands have close relatives
- Aka little gene flow b/w islands
- Many species only found on these island
Limited Gene flow means?
- Genetic material not being transferred b/w different pops
Adaptive Radiation
- Process where organisms diversify rapidly from ancestral species into many new forms
- I.e. Galapagos Finches, came from a gene that affected beak shape
Heritability
- Traits, heritable…
- Nat sel can occur without heritability, evolution CANNOT
Scientific Theory
- Explanation about some aspect of natural world
- Stood test of time from constant testing, held true every time
