Natural Selection Flashcards
What are fossils?
The ‘remains’ of organisms from millions of years ago, which are found in rocks
What are the 3 main ways that fossils are formed?
1 ) Gradual replacement by minerals
- Decay really slowly
- Replaced by minerals
- Form rock-like substances
- Dig them up
- Separate from rock
2) Casts and impressions
Casts:
- Organism buried in soft material (clay)
- As the clay hardens (organism decays)
- Left with gap same size and shape as the organism
Impressions:
- Footprint that stays there for a very long time
3) Preservation (no decay)
- Organisms stuck in amber or tar pits
- No oxygen or moisture, no decay takes place and organism remains completely in-tact
- Can happen in glaciers (too cold) or in peat bog (too acidic)
What are some reasons why a species might go extinct?
- Environment changes too quickly
- Habitat cut down
- New predator
- New disease
- new species outcompetes them
- Catastrophic event
Why are fossils used to as evidence for evolution?
Fossils show us how species have changed over millions of years
Why is the fossil record incomplete?
- Some organisms are soft-bodied so do not fossilise well
- Some fossils formed long ago may have been destroyed since
What is the Linnean system?
New type of classification system created in the 1700’s by Carl Linneus, based on characteristics and bone structure
What are the groups of the Linnean system?
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
What is the Binominal system?
Where you name species based on their genus and species name
What is the Three Domain System?
Introduced by Carl Woese
- Eukaryota
- Bacteria
- Archaea
What are evolutionary trees?
Evolutionary relationships between different species or groups ‘common ancestors’
What do the branch points show on an evolutionary tree (circled red in the above diagram)?
The divergence of a single population/species into two separate populations/species
What is selective breeding?
Take the best plants or animals and breed them together, in the hope of getting even better offspring
What is the process of selective breeding?
- Select the thing you want to breed that has the characteristics you’re after
- Breed them together
- Then again, out of the offspring, choose the most desirable characteristics
- Breed again
You do these steps for all generations, to get the characteristics that you desire
What are some drawbacks of selective breeding?
- Reduces the gene pool of the population
- Can sometimes lead to inbreeding (makes offspring particularly prone to diseases and defects)
- Less variation within a population
What is a gene pool?
Collections of all the alleles of an entire population
What is genetic engineering?
- Find one organism that has the desired characteristic
- Pick the gene responsible for that trait
- Transfer that gene to another organism, so that organism will develop the same trait
This is modifying the organism’s genome
You can call this organism genetically modified
What is gene therapy?
To use genetic engineering to treat inherited disorders
- You give a person a healthy version of the gene in hope that it will fix the problem
What are some problems of gene therapy?
- The faulty gene will be in all cells - would have to transfer the new gene into every cell of the body
What are pros and cons of genetic engineering using crops as an example?
Pros:
- Crops with more desirable characteristics
- More fruits
- Resistant to disease
- More food for less money
- Important in developing countries
Cons:
- Don’t know how genetically modified plants might affect our health
- Plants might make themselves into the wild, and outcompete other plants and change the whole ecosystem
What are the steps for genetically engineering?
- Find gene that you want
- Cut that section of DNA out to isolated, done with enzymes
- Insert gene into a vector (could either be a virus or a bacterial plasmid)
- Introduce vector to whichever organism we want to have the gene
- Organism cells will take up the vector and the genes it contains
- Start producing the protein that the gene codes for
