Unit 2: Evolution Flashcards
How did life begin?
1) Creation of organic material
- Major building blocks of life
- Miller-Urey experiment showed this was possible
2) Combining organic molecules to make polymers
- Small molecules combine to make big molecules
3) Create a self-replicating molecule
- RNA was probably the first genetic material
- RNA can encode information and work as an enzyme
4) The self-replicating molecule enters a membrane
What was the old, wrong idea of how life began, and how was it disproved?
Spontaneous generation = The idea that life often begins from non-living molecules
Louis Pasteur = scientist who disproved spontaneous generation
- Boiled broth (to kill bacteria) in a flask with a curved neck (= “swan neck”)
- Curved neck allowed flow of air in and out
- Curved neck did not allow bacteria to enter - No bacteria grew
- Proved bacteria do not spontaneously generate - When he broke the flask’s neck, bacteria grew
- Bacteria could get in and the soup was still good
What is the endosymbiotic theory, and what is the process of endosymbiosis?
Endosymbiotic theory: explains how eukaryotes evolved
- Endo = inside
- Symbiotic = help each other
Process of endosymbiosis
- A big prokaryote tried eating a small prokaryote and failed to digest it
- Small prokaryote gained protection and big prokaryote gained an organelle
a. Began a symbiotic relationship
i. Mitochondria useful to get rid of oxygen, which can be poisonous
ii. Chloroplast useful to make food from the sun
What are the evidences of endosymbiotic theory?
Evidence for endosymbiosis
● Mitochondria and Chloroplast probably began as small prokaryotes
● Mitochondria and Chloroplasts both:
1) Have 70S ribosomes
2) Have their own DNA (naked and circular)
3) Divide by themselves using binary fission
4) Have two membranes
5) Are 1 - 10um
What are the definitions of:
- Species
- Population
- Mutation
- Evolution
- Speciation?
- Species: a group of organisms capable of successfully interbreeding
- Population: a group of organisms of one species at one time at one place
- Mutation: a change in the DNA sequence
- Evolution: a change in the heritable characteristics of a population over time
- Speciation: evolution resulting in a new species
What does evolution by natural selection require?
Evolution by natural selection requires:
1) variation between individuals
2) hereditary characteristics
3) struggle to survive (caused by competition or environmental change)
What are the sources of genetic variation?
1) Mutation: Mutations add new DNA to a population
2) Meiosis: What DNA is put in a sperm/egg is somewhat random
3) Fertilization/sexual reproduction: Which sperm meets which egg or which people meet is random
Describe the process of natural selection.
- There is a variation between organisms in a population
- Those variations are heritable
- Individuals compete for food, mates, territory
- Individuals with more useful variations are more likely to survive and reproduce
- Useful variations are called Adaptations - They will have more offspring, so their DNA will be more common in the next
generation - This is evolution: a change in the heritable characteristics of a population over time
Describe the finches of Daphne Major as an example of natural selection.
Finches of Daphne Major
1. Finches (a type of bird) were discovered on the Galapagos Islands by Darwin
- There are several species of finches on the islands
- The different species have different beak sizes adapted to different types of food
2. Originally one species of finches arrived on the Galapagos
- It had little competition, so it’s offspring survived and colonized Daphne Major
3. The offspring had variation in their beak size and shape
- This was hereditary
4. Different beaks are better at eating different foods
- Ex. Big beaks are good for nuts
5. Those with well-adapted beaks were more likely to survive and reproduce
- Had more surviving offspring so their DNA and traits were more common in the next
generation
6. This is evolution by natural selection
When the environment changed due to a drought, larger beaks were selected for and the population evolved by natural selection
Describe antibiotic resistance in bacteria as an example of natural selection.
- Antibiotics kill prokaryotes (bacteria), but not eukaryotes
- So, they are often used to cure diseases in humans
- Example antibiotic = penicillin - Some bacteria are naturally more resistant to antibiotics than others
- This is hereditary/genetics - When antibiotics are used (= change in bacteria’s environment), bacteria with more resistance are more likely to survive and reproduce
- They have more offspring so their DNA and resistance is more common in the next generation - This is evolution by natural selection
“Superbugs” (bacteria resistant to many antibiotics) are becoming a big problem
What is adaptive radiation?
Adaptive radiation: When a single population evolves into several species/groups adapted to different habitats and conditions
What are the 3 main pieces of evidence for evolution?
The 3 main pieces of evidence for evolution are:
- Fossils
- Homologous structures
- Selective breeding
Describe fossils as one of the main pieces of evidence for evolution.
Fossils
- Fossils are the preserved remains of organisms
- Fossils show organisms species that are now extinct
- Suggest that DNA has changed over time
- Example) Non-avian Dinosaurs - Fossils show species between two other species
- Show gradual change over time
- Example) Horse evolution - Fossils ages are determined based on their relative position and using radiometric dating
Describe homologous structures as one of the main pieces of evidence for evolution.
Homologous structure
- Same basic structure
- Used for different purposes
- Many organisms share the similar structures that have been adapted to be used in different ways
- Suggests common ancestry (got the structure from a shared ancestor)
- More similar organisms are more closely related
- Shows adaptive radiation as the same structure is used for different things
Example: Pentadactyl limb = 5-finger bone structure on limbs of vertebrate
- Used for locomotion (Flying bats and grasping in humans)
Describe selective breeding as one of the main pieces of evidence for evolution.
Selective breeding
- Humans choose which organism/traits survive and reproduce
- Example) Choosing cows to make the most milk - Shows that genetic traits can change over time
- This is evolution by Artificial Selection
