Week 8-Evolution Flashcards
How are evolution and natural selection linked? Give an example
-These ideas date back to Darwin and the work he did observing different species of different members of the same species and the variation between them and why that might be.
-The environment cannot support unlimited growth – there’s a finite amount of space, air and food that organisms have to be in competition for and that the ones who are best adapted to the environment will win. So organisms vary in traits that have been selected in or out.
Example:
-Green beetles are more easily seen by birds that brown beetles, who can blend in to the soil, so green beetles are more likely to be eaten. Brown beetles survive and reproduce passing this trait onto their offspring=more brown beetles than green beetles in the population.
-We can say that the advantageous trait of having brown colouring has been selected in by a selection pressure, the predation by birds, and the beetles have been bred to have this colouring.
What are the 4 big principles of Evolution and natural selection?
- Principle of natural design for gene replication
- Superabundance
- Natural variation
- Selection pressures
Define the Principle of natural design for gene replication
We are a unique constellation of genes that drive physiological processes and behaviours. Evolution does not operate in individuals, rather evolution operates in genes. Genes giving us a genetic advantage need to make it to the next generation
Define Superabundance
Animals and plants produce more offspring than necessary. This is because at least one or more will be well adapted to the environment, survive, and pass on those genes.
Define Natural Variation
Each offspring is somehow different (unique gene combination produces different offspring variation=different likelihoods of surviving an environment.)
Define Selection Pressures
a) Natural selection pressures: Organisms must ensure that the genes survive so they can make it to the next generation
-Natural pressures=predation of beetles by birds
-Imposed pressures=selective breeding in dogs
Selection pressure: predation, susceptibility to disease and toxins, dangerous environment
-Organisms respond to these pressures through ADAPTATIONS
-BUT adaptations tend to have a trade off price to pay as the smaller the trade off the better the adaptatio
Define the Environment of evolutionary adaptiveness (EEA)
How the environment was when we evolved
-We can estimate and look at what the environment and selection pressures were like back then by looking at traits that occur universally, like the brown on the beetles, by looking at things that happen with everyone and was evolved and an advantage.
What behaviours or traits occurring universally in all cultures, are good candidates for evolutionary adaptations?
-The ability to infer others’ emotions (to determine if they’re a threat)
-To discern kin from non-kin (important for mating as mating within family is bad in terms of genetics)
-To identify and prefer healthier mates (to pass genes on)
-To cooperate with others (important for working in groups and group benefits)
Why can humans compete with other species?
-Agile hands: Can use tools
-Colour vision: Can detect opportunities and dangers
-Mastery of fire
-Bipedalism(walk on 2 feet): Walk long distances, carry tools, food and infants
-Linguistic abilities: Pass information, make plans, form complex civilisations
-Large complex brain has the power to do all of the above
What 2 facts were not understood at the time when Darwin (1809-1882) created the theory of evolution?
- Why members of the same species differ from one another, we are actually all different
- How anatomical, physiological and behavioural traits are passed from parents to offspring
-An unread manuscript in his files contained the answers , it had been sent to him by an Augustinian monk called Gregor Mendel, unfortunately for both the significance of mendel’s research was not recognised until the early part of 20th century
How did Mendel begin his studies on heredity?
-Mendel began his studies on heredity using mice. He was at St. Thomas’s Abbey but his bishop did not like one of his friars studying animal sex (mice), so Mendel switched to plants.
-Mendel also experimented with hawkweed (Hieracium)[32] and honeybees. He published a report on his work with hawkweed,[33] a group of plants of great interest to scientists at the time because of their diversity. However, the results of Mendel’s inheritance study in hawkweeds was unlike his results for peas; the first generation was very variable and many of their offspring were identical to the maternal parent.
-In his correspondence with Carl Nägeli he discussed his results but was unable to explain them.[32] It was not appreciated until the end of the nineteen century that many hawkweed species were apomictic, producing most of their seeds through an asexual process.
-None of his results on bees survived, except for a passing mention in the reports of Moravian Apiculture Society.[34] All that is known definitely is that he used Cyprian and Carniolan bees,[35] which were particularly aggressive to the annoyance of other monks and visitors of the monastery such that he was asked to get rid of them.[36] Mendel, on the other hand, was fond of his bees, and referred to them as “my dearest little animals”.[37]
What are Dichotomous traits and how did Mendel study this?
-Mendel (1822-1884) studied inheritance in pea plants
-He studied dichotomous traits, and he began his experiments by crossing the offspring of true breeding lines.
-DT: These are traits that occur in one form or the other, never in combination: eye colour in humans or pea colour in peas
What are True Breeding Lines?
-They are breeding lines in which interbred members always produce offspring with the same trait, generation after generation. In the pea case it would be green seed or yellow seed.
-Mendel crossed 2 different true breeding lines and then their offspring. One trait, dominant traits, appeared in all of the first generation offspring. The other trait which he called the recessive trait, appeared in about one quarter of the second generation offspring.
-Pure-bred dogs have identical offspring
-dominant=yellow recessive=green
Define Genotype and Phenotype
G: It’s the combination of alleles on organism inherited from its parents (genes)
P: It’s the organisms appearance (physical) (i.e., an organism’s observable trait)
-2 people with straight hairlines cannot pass widows peak on to offspring (2x ww)
What was Mendel’s first idea to explain his results?
There are two kinds of inherited factors for each dichotomous trait - today the inherited factor is called gene.
What was Mendel’s second idea to explain his results?
Each organism possesses 2 genes for each of its dichotomous traits. In the case of widow’s peak the genes would be W and w
-2 genes that control the same trait are called alleles (in case of pea colour would be Yellow and Green, in case of widow’s peak would be W and w).
-Organisms that possess 2 identical genes for a trait that are said to be homozygous and those possess 2 different genes for a trait are said to be heterozygous for that trait.
What was Mendel’s third idea to explain his results?
One of the two genes for each dichotomous trait dominates the other in heterozygous organisms
What was Mendel’s fourth idea to explain his results?
Dichotomous trait, each organism randomly inherits one of its father’s two factors and one of its mother’s two factor (we know this happens randomly as otherwise everyone in a family would look the same)
What are chromosomes?
-Not until the early 20th century, genes were found to be located on chromosomes
-Chromosomes occur in matched pairs (with ONE exception aka pair 23), and each species has a characteristic number of pairs in each of its body cells
-Humans have 23 pairs
-The two genes that control each trait are situated at the same location (loci), one on each chromosome of a particular pair
What are Sex chromosomes and sex-linked traits?
-There is only one exception to the rule that chromosomes always come in matched pairs
-Traits that are influenced by genes on these chromosomes are referred to as sex linked
-Traits that are controlled by genes on the sex chromosomes occur more frequently in one sex than the other
-If the trait is dominant it will occur in females because females have twice the chance of receiving the X chromosome
-Recessive sex linked diseases occur more frequently in males (Haemophilia, colour blindness)
-Gene for blood clotting is on X chromosome so more likely in males if one damaged X chromosome
-Turners syndrome (just one X chromosome in females)
What is meiosis?
-The process of cell division that produces gametes (egg or sperm cell) is called meiosis
-Chromosomes divide, and one chromosome of each pair goes to each of the two gametes that result from the cell division
-Information is shared and crossed over
-Sperm + egg = zygote
