B4 - natural selection and genetic modification Flashcards
Define evolution
A gradual change in the characteristics of a species over time
What is the genus of a binomial name
Capital letter
Eg. Homo (in Homo sapiens)
What is the species in a binomial name
Lowercase letter
Eg. sapien (in Homo sapiens)
Why can’t scientists be certain species evolved from one another
Gaps in fossil records
How are stone tools dated from their environment?
Scientist date, the layers of sediment where the stone tool was found
Ardi (Ardipithecus ramidus)
- 4.4 million years ago
- 1.2m tall, 50kg
- leg bones suggest upright walking
- long arms and long big toes suggest tree climbing
Lucy (Australopithecus afarensis)
- 3.2 million years ago
- arched feet (walking not climbing)
- toes more curved than modern arrangement
- leg bones and feet suggest walked more efficiently than Ardi
Handyman (Homo habilis)
- 2.4-1.4 million years ago
- short height, long arms, walked upright
- smaller face and teeth than Lucy
- thought to be the first makers of stone tools
Homo Erectus
- 1.6 million years ago
- tall and strongly built
- short arms and long legs (more human like)
- walk upright
- developed and used stone tools
Homo sapiens
- 195,000 years ago - present
- evolved from Africa
- lighter build skeleton
- less heavy jaws and smaller teeth
What are humans and ancestors called
Hominids
How have stone tools created by human-like species developed over time
They have increased in complexity
Why might stone tools have become more complex over time
- changes in hunting techniques
- increased intelligence and dexterity (supported due to increasing brain sizes)
Causes of genetic variation
Sexual reproduction and mutations
What is evolutionary fitness
Ability to reproduce and survive in an environment
How do adaptations allow species to survive
Animals with characteristics that make them better adapted to selection pressures in their environment have a better chance of survival and so are more likely to breed successfully
What is a selection pressure, give eg
Factors that affect an organisms chance of survival and reproduction
Eg. Predation, competition and disease
How can natural selection lead to the evolution of new species
- organisms with advantageous characteristics breed, and pass on the useful alleles
- This process causes species change over time
Which scientist had theory of natural selection and evolution?
Charles Darwin
How does the development of resistance in organisms support Darwin’s theory?
- Random mutations in the DNA of bacteria, cause antibiotic resistance
- When the host gets treated with antibiotics are non-resistant bacteria, die out, leaving a population of mostly resistant bacteria
- The resistant bacteria reproduce passing on the resistant allele, which becomes more common in the population over time
How were organisms originally classified?
According to similarities and differences in their observable characteristics
- As technology improved, this came to include cell structure
Then they are subdivided into smaller groups of common features and DNA
order of the five kingdom classification system
Kingdom
Phylum
Class
Order
Family
Genus
Species
King prawn curry or fat greasy sausages
What are the five kingdoms?
- Animals
- Plants
- Fungi
- Prokaryotes
- Protists
Characteristics of animals
- multicellular
- Cells have nuclei
- No cell walls
Characteristics of plants
- multicellular
- chloroplasts for photosynthesis
- Cells have nuclei
- Cellulose cell walls
Characteristics of fungi
- multicellular (apart from yeasts)
- Cells have nuclei
- Cell walls contain Chintin not cellulose
Characteristics of protists
- Mostly unicellular
- Cells have nuclei
- Some have cell walls (not made of chintin)
-Some have chloroplasts
Characteristics of prokaryotes
- unicellular
- Cells don’t have nuclei
- Flexible cell walls
What is genetic analysis?
Determining and comparing the sequences of DNA bases in organisms
Why are organisms now classified into three domains?
It was found that some organisms in the prokaryote kingdom weren’t is closely related as originally thought
What are the three domains?
- Eukarya
- Bacteria
- Archaea
Characteristics of eukarya
Cells with a nucleus and genes with a unused sections of DNA
Characteristics of bacteria
A cell without a nucleus, and no unused sections of DNA
Characteristics of archaea
A cell without a nucleus and genes with unused sections of DNA
Why are new breeds and varieties selectively bred?
- disease tolerance
- Greater crop yield
- Size
- Pet characteristics (dogs)
- Fertility (sheep)
What is a genetically modified organism (GMO)?
modifying the genome of an organism by introducing a gene from another organism to result in a desired characteristic
How is selective breeding carried out?
- Select organisms possess the desired characteristics
- breed them with each other
- Select the best offspring and breed them together
- Continue this process over several generations, so the desirable trait get stronger and eventually all offspring will have the characteristic
Risks of selective breeding
- Gene pool is reduced (animals are closely related: inbreeding)
- Health problems due to increase chance of inheriting genetic defects
- Lack of variation, if a new disease appears less chance of resistant alleles, if one organism dies, the others are likely to as well (closely related)
What is the restriction enzyme?
Enzymes that recognise specific sequences of DNA, cut the DNA at these points, leaving the DNA with sticky ends
What are ligase enzymes?
Enzymes are used to join two pieces of DNA together at the sticky ends
What is recombinant DNA?
Two different bits of DNA stuck together
What is a vector?
Something that is used to transfer DNA into a cell (a carrier of something)
Examples of vectors in genetic engineering
Plasmids and viruses
What are plasmids?
Small molecules of DNA that can be transferred between bacteria
Why can viruses be used as vectors?
Insert DNA into organisms, they infect
The stages of genetic engineering of bacteria
- gene wanted for insertion is cut open by restriction enzyme left with sticky ends
- vector DNA is cut open with same restriction enzyme left with sticky ends
- Ligase enzymes are used to join these pieces of DNA, making recombinant DNA
- recombinant, DNA inserted into bacterial cells, which replicate the gene as they can reproduce quickly
How are bacteria used to make insulin?
Genetic engineering process
Bacteria containing the gene for human insulin can be grown in large numbers in a fermenter
What happens at sticky ends?
- Restriction enzymes leave single strands of DNA with unpaired bases
- Ligase enzymes match bases with complementary bases on the other sticky end
Advantages of GM, golden rice
Greater quantity of vitamin A helps eyesight
Disadvantages of GM, golden rice
Worries that it may damage, food chains or human health
Advantages of GM, herbicide resistant plants
Increases crop yield as weeds are killed, but the plants can survive
Disadvantages of GM herbicide resistant plants
The gene may be picked up by weeds, creating a new ‘super-weed’ variety
Advantages of GM insulin
Can be produced in large amounts to meet demand
Disadvantages of GM insulin
Can’t be used by all diabetics, as it is not the same as insulin from mammals
Disadvantages of selective breeding
- Takes much longer than genetic engineering
- Animals might not necessarily pick up desired characteristic (chance)
Benefits of genetically, modifying over selective breeding
- genes are changed directly
- Much quicker
- Organisms are more likely to gain the desired characteristic
