IVE - Mendel, Darwin, Wallace and Lamarck Flashcards
(23 cards)
What is Mendel considered?
The founding father of genetics
Who was Mendel?
Austrian scientist and monk who lived in the 1800s.
Around Mendel’s time, farmers understood that
cross-breeding could result in plants with more desirable traits, but didn’t understand why.
What did Mendel experiment with?
pea plants
Example 1 of one of mendel’s experiments: green and yellow pod pea plants
He cross bred a pea plant with green pods, and a pea plant with yellow pods, and all the offspring were yellow podded.
Next he took two of the offspring, and cross bred them, but this time, 1/4 of the offspring were green, and 3/4 were yellow.
What did Mendel discover?
He found out what he called ‘hereditary units’ which could be recessive or dominant.
The recessive hereditary units could only be expressed if both parents of the offspring had it.
The green pod’s hereditary unit was recessive whereas the yellow pod’s hereditary unit was dominant.
Mendel found that this applied to different characteristics as well such as…
height and colour of flowers - multiple characteristics were being passed down in this dominant, recessive way.
What is meant by a variation?
A mutation that occurs in the genome of the organism that actually varies, i.e. alters their phenotype.
Beneficial mutations
Charles Darwin observed that some of these mutations donated characteristics to members of a species that allowed them to survive easier. This was known as the ‘survival of the fittest’
Natural selection
the fittest individuals were being selected to survive
evolution
inheritence of certain characteristics in a population, over multiple generations could lead to a change in the entire species, or form a new species.
what does the theory of evolution suggest:
all life forms evolved from simpler, one-celled organisms that first developed on earth.
Why did it take a long time for Darwin’s theory to be proved?
Religious reasons - Darwin’s theory challenged the religious belief that God created all life forms.
Lack of evidence - a lack of hard evidence made many scientists hesitant to accept Darwin & Wallace’s theory.
DNA hadn’t been discovered yet - the mechanism for inheritance and variation, now understood through genetics, was unknown during Darwin’s time.
Proof of evolution:
fossils
antibiotic resistant strains of bacteria
when can we say that a new species has been formed?
when the variations have created organisms that can no longer interbreed with their ancestor.
Series of events that may have led to zebra evolving to be faster:
There is variation among the zebra population so that some can run faster than others
A mutation arises that allows some zebras to run faster
Those zebras that can run fastest are more likely to survive…
…and are therefore more likely to reproduce and pass on their advantageous alleles
This repeats over multiple generations
So the advantageous allele spreads throughout the population, until the species has ‘evolved’ to run faster
Speciation:
the process by which populations evolve to become distinct species.
Lamarck’s theory:
suggested that organisms can acquire new traits during their lifetime, and these could be passed on to their offspring.
According to Lamarck’s theory, how did Giraffes acquire long necks:
- they started with short necks adapted to shorter vegetation
- they stretched their necks to reach higher trees, resulting in longer necks during the lifetime of the individual
- the longer neck trait was passed onto their offspring
Lamarck’s theory was proven wrong by…
modern genetics
According to Darwin and Wallace’s theory why do Giraffes have long necks?
Some giraffes had longer necks than others, due to variation within the species.
Giraffes with longer necks were better adapted to their environment, as they could eat leaves from taller trees.
Giraffes with longer necks had a higher chance of surviving and reproducing, and passed on the trait of long necks to their offspring.
Over many generations, this process produced modern giraffes, with very long necks.
Darwin and Wallace came to their conclusion through:
Individual organisms within a species show a wide range of variation for a specific trait.
Darwin observed variations between species adapted to different environments.
Older layers of rock contained fossils of less complex organisms, while more recent layers showed more complex organisms.
Darwin and Wallace published their findings
together, although they arrived to the same conclusion individually.
