Evolution Flashcards
What is Charles Darwin’s book called?
The origin of species
what is Charles Darwin’s theory called?
Natural selection
Evolution by natural selection
Organisms produce more offspring than can survive
Organisms compete for limited resources
Individuals of a population vary extensively
Much of this variation is heritable
Individuals that are better suited (pre-adapted) to local conditions survive to produce more offspring.
Processes for change are gradual
The changes in populations can be viewed as descent with modification, as the change does not demonstrate progress (improvement). It is simply change.
Darwin’s Observations and Questions (Observations)
Some of Darwin’s observations that led to his theory were:
The flora and fauna were different in different regions
He found fossils of extinct animals that looked similar to living animals
Finches found on islands resembled continental finches but were different in some characteristics
Finch beaks were adapted to the food source on each island
Darwin’s Observations and
Darwin’s’ Observations and Questions (Questions)
Questions that Darwin considered:
Why were all types of organisms not randomly distributed?
Why would living and fossilised organisms that looked similar be found in the same region?
Why did the Galapagos species so closely resemble organisms on the adjacent South American coastline?
Could species have been modified from an ancestral form that arrived on the Galapagos Islands shortly after the islands were formed?
extinct
a species that has completely disappeared from earth completely
what is an adaption?
a change in psychological, behavioral, or physical characteristics in a species overtime (helps them survive)
how does an adaption occur?
Result of random, heritable mutations in DNA
Accumulate over generations
what is a variation within a species?
Structural, functional or physiological differences between individuals
As becomes more common - considered trait of characteristic of population
what is mimicry?
a type of structural adaptation. Harmless species physically resemble a harmful species. Predators avoid the harmless species as much as they do the harmful one.
What happened to the English Peppered Moth?
They have three colours (greyish/white with black dots, black, or somewhere between these two)
in 1848 the black ones made up of 2% of the population in Manchester
then the brits went through the industrial revolution and the black ones swarmed
they made up 95% in the city and less in rural areas
Variation within species
Created by the different combinations of genetic information (alleles) that offspring inherit from their parents.
Source of all those different alleles is mutation
Mutation
Permanent change in the genetic material of an organism
Only source of new genetic variation
Selective Advantages
Improves an organism’s chances of survival in changing environment and reproduction
Mutation as become beneficial
Rapid Reproduction & Selective Advantage
Species that reproduce quickly adapt quickly to changing conditions.
Bacteria and some insects reproduce quickly
Mutated allele that could be an advantage is passed on to help the population survive
Examples: Staphylococcus aureus bacteria
Selective Pressure
An abiotic (non-living) or biotic (living) environmental condition can be said to select for certain characteristics in some individuals and select against certain characteristics in others. This is how the environment exerts a selective pressure on a population.
Selective pressure can result from any number of abiotic or biotic factors
Examples of selective pressures include:
(Temperature change / climate conditions, Diseases, Light level change, Change in predators , Change in competition)
These selective pressures can result in different patterns of natural selection
what does natural selection not do?
anticipate change in the environment (that’s why climate change is a no no)
fitness
Contribution an individual makes to next generation by producing offspring that will survive long enough to reproduce
High degree of FITNESS, organism survives and reproduces to pass along advantageous genes
Number of re productively viable offspring that organism produces
what is directional selection?
This occurs when changing conditions cause allele frequencies to shift so that individuals at one end of the spectrum become more common
what is an example of directional selection?
When insect populations develop genetic resistance to being sprayed with pesticides
This type of natural selection occurs during periods of environmental change
what is stabalizing selection
When environmental conditions are stable and are not changing much
Most organisms in a population are well adapted to the conditions
Natural selection will tend to eliminate individuals on both ends of the genetic spectrum
disruptive or diversifying selection
This occurs when conditions favours individuals at both ends of the genetic spectrum
Organisms that have intermediate traits are at a disadvantage
Can cause populations to split and potentially form new species
Artificial Selection
A common example of artificial selection is the food crops produced from the wild mustard plant. With careful selective breeding, the one original plant has been developed into many different crops.
The impact of artificial selection can be enormous
In an experiment begun in 1896, corn was selected for oil content
Corn with the highest and the lowest oil content were both selected for and allowed to reproduce
Examples of Artificial Selection
Cats bred for appearance
Cows bred to increase muscle for meat consumption
Chickens bred to produce more eggs
By selecting the parents that carry the genetic material that breeders are interested in, cat breeders have produced cats with distinct features. All the cats shown above carry the same kinds of genes (e.g., fur, size or length) However, the alleles for these genes differ among the cats, allowing humans to select for or against particular traits
biotechnology
Use of technology and organisms to produce useful products
Consequences of Artificial Selection
When a particular trait is selected for exclusively, often other traits become negatively affected
Example: English bulldogs are bred to have flat faces. Many of the breed suffer from respiratory problems.
Artificial selection often decreases genetic diversity in a population
Makes the population less fit for environmental changes and natural selection
Artificial selection in agriculture is often used in monoculture planting, where a large area has one type of plant with little genetic diversity
Is easier to manage
High risk that any environmental change, such as a new disease, could wipe out the crop
Sexual Selection
Variation in ability to obtain mates
Sexual selection is natural selection for mating based on competition between makes and choices made by females
Favouring of any trait that specifically enhances the mating success of an individual
This type of selection often leads to males and females of a species evolving appearances and behaviours that are quite different from each other
Sexual dimorphism
Example: Male mallard vs Female mallard
Mating and courtship behaviours
