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What evidence exists to support the theory of Evolution? (5) (Lecture 1)
- Comparative embryology.
- Comparative anatomy.
- Palaeontology (transition fossils).
What is comparative embryology? (Lecture 1)
Study of embryos of different organisms. Scientists look for similarities between them.
In Comparative embryology, what do similarities between vertebrate species (chordates) infer? (Lecture 1)
- Similarities between chordates suggests that they share a common ancestor.
- Example: chordates share a gill pouch in embryonic form, however gills are only manifested in fish and amphibian larvae.
- Thus, the structure of embryos is very similar, but as they develop distinctive differences take shape to fulfil very different functions.
What is comparative anatomy? (Lecture 1)
The study of similarities and differences between structures in organisms. (Lecture 1)
In Comparative anatomy, what do similarities between structures in organisms (chordates) infer, give an example that is evidence of this? (Lecture 1)
- Common structures infers the existence of a common ancestor.
- Example is the pentadactyl limb (5 digit limb).
What is the pentadactyl limb and the lobe fin fish? (Lecture 1)
- Evidence that terrestrial animals possess a common ancestor in which they have inherited the pentadactyl (5 digit) limb.
- It is thought that humans, birds, bats, humans, whales, lizards, cows, frogs and others have inherited the common limb structures from the lobe fin fish.
Describe Palaeontology as evidence for evolution. (Lecture 1)
- Fossils occur mostly in sedimentary rocks, and since sedimentary rocks form in layers, there would be multiple layers of fossils embedded into these sedimentary rocks.
- Older fossils are in the deepest layers.
- Examining fossils across layers is evidence of how organisms have changed over time.
- It in essence is a timeline of evolution, however fossil records are incomplete, rare and there is not a smooth transition between each group showing how they evolved.
What are transitional fossils? (Lecture 1)
- Transitional fossils show how one animal group shifted from one type to the other.
- Example: Acheopteryx linked birds and reptiles.
- Appearing 150mya it was similar to both species, with a long tail, claws, solid bones and teeth. It had a wishbone and feathers, like birds.
What is bio-geography? (Lecture 1)
- Study of geographical distribution of living things and fossils.
- Used by Darwin and Wallace for evidence of evolution.
Explain bio-geography as evidence for evolution. (Lecture 1)
Darwin observed that day-animals were similar to the fossils that were found in their habitats. He also noted that different regions had their own distinct flora and fauna.He deduced that those species evolved from a common ancestor in that region and evolved to suit the environment.Proposed that where living things had been separated for a long time there would be a more significant difference between them.
Explain biochemistry as evidence for evolution. (Lecture 1)
- Examining molecules and amino acid sequences reflects how closely related a species is.
- This method shows that humans are more closely related to chimpanzees than gorillas.
- Mixing blood also helps determine how closely related a species is because closely related species have a smaller antigen-antibody reaction.
- Can also be compared using DNA sequencing techniques. Nucleotide sequences in stands of DNA, from different species are compared and the more similar the DNA sequences are the more closely related the species.
Who was Gregor Mendel? (Lecture 2)
- 19th Century Monk.
- Taught maths and physics but is best known for his work in understanding inheritance.
- Conducted experiments with garden peas to look for patterns of inheritance.
- Known as the "father of genetics" despite no prior works on biology.
What was the understanding of inheritance prior to Mendel? (Lecture 2)
The understanding prior to Mendel was that the characteristics of parents blended to give the characteristics of the offspring.
Describe Mendel's experiments. (Lecture 2)
- He examined characteristics of pea plants e.g. round/wrinkled seed.
- He bred each characteristic for two years to achieve pure breeding lines - we now call this homozygous for the trait.
- He then crossed one variety with another by using a paint brush to take pollen from the male part of the plants (anther) and transfer it to the female part (stigma).
What was a problem Mendel faced when trying to have homozygous plants reproduce? (Lecture 2)
- He had to control self-pollination or the plant would asexually reproduce.
- He removed male and female parts of plants as a result to stop this.
- He also regulated cross pollination by using a paint brush to transfer pollen onto the stigma of other plants.
What did Mendel do with his experiments to make sure they were valid and reliable? (Lecture 2)
- Reliable: Repeated his experiments many time and kept meticulous records.
- Valid: Studied only one characteristic at a time, and controlled self and cross pollination.
What were Mendel's findings and what was his conclusion? (Lecture 2)
- He found that when he crossed a true-breed yellow with a true-breed green the first generation offspring were all yellow.
- In the second generation he found a ratio of 3:1 to yellow to green.
- He concluded that: each trait is determined by units or "factors", as he called them, that are passed onto descendants unchanged.
- We now call these genes.
- An individual inherits one unit from each parents and while one of those may not show up physically, it can be passed onto the next generation.
Why was Mendel's work overlooked? (Lecture 2)
- The limited understanding other scientists had of cells, mitosis, meiosis, chromosomes, etc, made his work hard to understand, and too progressive for the time.
- Furthermore it contained a lot of maths which was unusual for biology and easily disregarded (or not understood)
- Did not have any prior research and thus no reputation.
What is reproductive technology and why is it used? (Lecture 3)
It is the use of technology to assist and improve reproduction.
Outline brief history of reproductive technology. (Lecture 3)
- The change from hunters and gatherers to farming was the beginning of genetic modifications.
- Farmers selected seeds from desirable plants and planted them in crops, reducing the genetic variation in the plants they grew.
Outline reproductive technology nowadays in agriculture. (Lecture 3)
- Similarly bred cattle to obtain a population that provided farmers with desired characteristics: high meat yield or milk production.
- This is use of selective breeding: the selection of organisms to breed for specific traits.
How does selective breeding differ from natural selection? (Lecture 3)
Selective breeding is different as in natural selection it is the environment that selects for certain traits whereas in selective breeding, humans select the traits manually.
How does selective breeding take place in plants an animals? (Lecture 3)
- Plants; artificial pollination.
- Animals; selecting animals to breed, or by artificial insemination.
What is artificial pollination? (Lecture 3)
Involves the removing of stamens of a flower and dusting the pollen onto the stigma of that flower or another flower.
Give an example of selective breeding within animals. (Lecture 3)
Animals are selected based off their desired characteristics e.g. high yielding creamy milk is achieved through breeding a Friesian cow with a Jersey cow.
What are ways in which selective breeding can go wrong? (Lecture 3)
- Offspring can have traits that are detrimental to the animal e.g. a cow cannot support the size of their udder, as so much milk is produced.
- Expensive and time consuming in transporting animals. This is why artificial insemination is favourable.
What is artificial insemination and how is it preferable over selective breeding? (Lecture 3)
- Process in which semen is collection from a male (bull) and transferred to a female (cow).
- The semen is collected using mechanical stimulation and stored in liquid nitrogen, making it easy to transport.
Advantages and disadvantages of artificial insemination. (Lecture 3)
- Transporting semen is much quicker and less expensive than transporting livestock.
- Many cows can only be inseminated from one bull.
- Artificial insemination can assist with reproduction of endangered species.
- It does result in reduced genetic variation.
What is cloning? (Lecture 3)
Producing a genetic copy of another organism.
What is Reproductive Cloning? (Lecture 3)
Creating a whole organism that is a clone of another organism.
What is Therapeutic Cloning? (Lecture 3)
Involves producing embryonic stem cells which can then be grown into specific tissue.
What is Gene Cloning? (Lecture 3)
Cloning individual genes -- used in genetic engineering.
Describe cloning in plants. (Lecture 3)
Is very simple and has been used for centuries. Talking cuttings from plants produces clones.
Describe cloning in animals. (Lecture 3)
- Mature cells from the udder of an adult sheep.
- First mammal to be cloned was Dolly the sheep.
- Only the female sheep was used.
Outline the process creating Dolly the cloned sheep. (Lecture 3)
- (1) Donor cell is taken from sheep's udder.
- (2) An egg cell is taken from an adult female sheep.
- (3) The nucleus of the cell is removed.
- (4) These two cells are fused using an electric shock.
- (5) The fused cell begins dividing normally.
- (6) The embryo is placed in the uterus of a foster mother.
- (7) The embryo develops normally into a lamb -- Dolly.
Describe cloning now: one advantage and disadvantage. (Lecture 3)
- The advantage of cloning is that the genetic make-up of an organism is easily predicted, and thus no mistakes occur that do in selective breeding.
- A disadvantage is the reduced genetic variation population, that may not survive an environmental change.