1. Evolutionary Theory Flashcards
What knowledge did early biologists lack about evolution?
They believed evolution as fact but did not know the mechanism (how it happened)
Jean Baptiste Lamarck (1744-1829)
Organisms within a species aspire to higher forms and this is this is passed onto future generations (inheritance of acquired characteristics) e.g. giraffes reaching for leaves
Erasmus Darwin (1731-1802)
Charles Darwin’s grandfather
Believed all living things could have a common ancestor, and competition might be the driving force
Charles Darwin - background
1809-1882
Studied medicine at Edinburgh university but quit
Studied for BA at Cambridge with the aim of joining the clergy
Became interested in biology and travelled around South America on HMS Beagle for 5 years working as a naturalist
Galapagos Islands…
Darwin noticed varied physical features of birds on different islands, and realised they were suited to their specific food source
Darwin was influenced by 2 people…
Charles Lyell: Victorian times, trying to understand geological changes over time
Thomas Malthus: overpopulation leading to survival of those most fit to survive
What is natural selection?
The mechanism for evolutionary change
3 parts to natural selection
- VARIATION - population of organisms must have a variety of traits
- INHERITANCE - traits must reliably inherited by offspring
- SELECTION - some traits must aid survival, so more likely that owner will reach maturity and have own offspring to inherit that trait
Peppered moths
Evolved to be camouflaged against trees
Industrial revolution - soot changed colour of trees
Variation within the group meaning one moth is the darkest - more likely to survive and pass on this trait
How gradual is natural selection?
New adaptations can take approximately 1,000 generations to become ‘fixed’ (in humans a generation is around 30 years, meaning 30,000 years for a new adaptation to become fixed)
What does it mean if an adaptation is ‘fixed’?
present in all members within a group
What did evolution start with?
We all share a common ancestor / life source from which we have evolved different traits
Why did Darwin not publish his theory for 20 years?
Due to its controversial nature
Alfred Russel Wallace…
Sent Darwin his own ideas about natural selection in 1858
He and Darwin presented their papers to the Linnean Society of London 1st July 1858
Darwin had more evidence and understanding
The Origin of Species
Published 1859
Presenting ideas about how the natural world came to be
Controversial - religious leaders
Still relevant today
Darwin’s thoughts on inheritance
He did not know. He thought of inheritance as being a blend of parents’ characteristics
Gregor Mendel’s work on inheritance was in 1866
Religious reaction
Contradicted some bible teachings (all living things were created by God)
Christians believed that humans are distinct from animals - Darwin said we share common ancestors
What does heterozygous mean in genetic inheritance?
An individual carries both copies of the dominant gene
What does homozygous mean in genetic inheritance?
An individual carries two copies of the dominant gene
When will an individual express a recessive gene?
When an individual is homozygous for the recessive gene (i.e. carries both copies of the recessive gene)
What did Mendel refer to genes as?
particles of heredity
How was Mendel’s work beneficial to Darwin’s theory of evolution?
It offered the mechanism by which traits are inherited
What is gene mutation?
A spontaneous change in DNA
What is ethology?
The study of behaviour from an evolutionary perspective
Levels of causality (Niko Tinbergen’s Four Whys)
- Proximate or mechanistic cause
- Developmental or ontogenetic cause
- Phylogenetic or historical cause
- Functional or ultimate cause
What is group selection?
Idea Darwin rejected that natural selection operates on groups and produces adaptations to benefit the group
Wynne Edwards (1962)
Animals restrain their own reproduction so that the food supply is not overeaten
However, a group member who did not restrain their reproduction would be better off than those who did
George C. Williams (1966)
Selection works on individuals within a population/species
What quickly replaces the notion of group selection?
The notion of individual selection
What did Richard Dawkins (1976) say about individual selection?
Genes are what are selected
Whose mathematical work introduced inclusive fitness?
William Hamilton
What is inclusive fitness?
We seek the best for our genes, whether they are in out own bodies or someone else’s (e.g. relative)
The more related to us someone is, the more we want to help them survive
What does inclusive fitness explain?
Parental care and kinship, which positively affect an individual’s inclusive fitness
What percentage of our genes do we share with our relatives?
50% with each parent and siblings
25% with grandparents/grandchildren
12.5% with first cousins
What does the ‘selfish gene’ mean?
Does not mean that genes are deliberately selfish, just that genes that are good at making further copies will be selected for
What is the Green Beard effect?
A gene for green beards which recognises and helps other organisms with that gene will prosper
What do the ‘selfish gene’ and the Green Beard effect explain?
it explains helpful behaviour (altruism) being due to selfish reasons (the propagation of the green beard gene)
What is Social Darwinism?
Founded by Herbert Spencer (came up with the misleading phrase ‘survival of the fittest’)
A range of ideologies about how natural selection can be applies to competition between human groups
What did Social Darwinism justify?
Social Darwinism justified social inequality as being due to superiority of certain humans - a view not supported by Darwin
What did Social Darwinism imply?
Social Darwinism implies ideas of racial superiority, particularly among white Europeans/Americans
How were ideas of Social Darwinism used?
They were put into practice by certain authorities and governments
What’s eugenics?
the study of human heredity patterns with the goal of improving the species through selective breeding
What is believed about eugenics?
It is believed that human health and intelligence would increase, resources would be saved and suffering prevented
What did eugenics include?
Selective breeding
Possibly genetic engineering
History of forced sterilisation
First practised in USA early 1900s
65,000 mentally ill, deaf and blind native Americans and criminals were voluntarily or forcibly sterilised
Three categories of forces sterilisation:
Eugenic
Therapeutic
Punitive
How long did sterilisation laws remain on the books for?
In 27 states sterilisation laws remained on the book in 1956
Nazi Germany
Eugenic programmes to ‘racial hygiene’
Protect the Aryan race from those identified as “life unworthy of life”
Included:
Forced sterilisation (400,000 people)
Incentives for breeding and controlled marriage
The Holocaust
3 misunderstandings
- What occurs in nature is what should occur
- Humans have no control over their evolutionary destiny
- Evolution is progress towards higher forms
Collecting evidence
Difficult, as it happens so slowly it can’t be measured (unless species with short lifespans)
We can only make predictions about what we can find now or from the past
Fossils
We see development of species over millions of years
Few animals fossilise - rare
Only certain body parts fossilise - we fill in gaps with behaviour
How could fossils be used to disprove evolution?
If one species appeared in the wrong era e.g. rabbit in the Precambrian
