Unit 3 - Evolution Flashcards
What are the 2 pre-evolution theories?
- The world was less than 10 000 years old and relatively unchanging
- Species are fixed or permanent and do not change over time from generation to generation.
What is Uniformitarianism?
Earth was formed entirely by the slow-moving processes of erosion and sedimentation (which are still ongoing today)- (this was supported and popularized by geologist Charles Lyell in 1830)
What did James Hutton do?
- James Hutton challenged the worlds “young age”
- By studying rates of present-day erosion and sedimentation, he concluded that it must have taken millions of years to form the current landscape.
What did George Cuvier discover?
- Fossils of ancient animals challenged the idea that species were fixed.
- Skeletons of elephants and mammoths were compared and similarities were found by Georges Cuvier
- Concluded that they were different enough to be different species but maybe of common ancestry
What is Lamarck’s theory of adaptation?
Jean-Baptiste Lamarck proposed that species change over time and that evolution occurs due to adaptation
What were Lamarck’s three guiding ideas on why species change?
- Use & Disuse: Gaining/losing characteristics depends on what is/is not used by an organism. (wrong)
- These acquired characteristics would pass on to offspring. (right)
- Perfection with Use & Need: All organisms strive for perfection (change and acquire characteristics in order to maximize their success in an environment). (wrong)
What were all the Flaws in Lamarck’s Ideas?
- Organisms cannot inherit characteristics that their predecessors “acquired” during their lifetimes.
- Characteristics that are inherited must be encoded in parental DNA and passed onto offspring.
- Although The idea of adaptation Evolution credited to Lamarck.
- Evolution involves the process of adaptation.
- Adaptation – inherited characteristic that improves an organism’s ability to survive in a particular environment.
What were Darwin’s observations on the pattern of diversity?
- Species vary globally
- Species vary locally
- Species vary over time
Explain species varying globally in Darwin’s theory.
- Distantly related species living in similar habitats, but in different parts of the world looked and acted similar (i.e. Australia has emus while Africa has ostriches; all are large, flightless birds)
- Some areas had unique organisms not found anywhere else in the world
Explain Species vary locally in Darwin’s theory.
- Related animal species that occupy different habitats (within a local environment) had different features
- Ex. The different islands of the Galapagos had vastly different climates, whereby Darwin discovered different finches that had possessed unique adaptations, allowing them to feed on particular food sources local to them
Explain species vary over time in Darwin’s theory.
- Species living today are descended from ancestral species
- Ex. Darwin discovered fossils of species that appeared very similar to modern-day animals
What is Thomas Malthus’ theory of competition?
- Darwin was also influenced by Thomas Malthus, who argued that the human population is growing at a faster rate than the rate at which supplies of food and other resources can be produced.
- Darwin realized that this idea could be applied to all species
- The above concepts are what enabled Darwin to develop his theory for the mechanism of evolutionary change.
Explain the 2 major points in Darwin’s theory?
- All Organisms Are Descended From Others
- Proposed the major concept of descent with modification
- Definition: descendants of the earliest organisms spread into various habitats over millions of years and accumulated different modifications or adaptations
- The term evolution now replaces ‘descent with modification’
- Descent with modification explains the diversity of life Ex. Insects with a common ancestor have different adaptations that allow them to survive in their unique environments (i.e. different camouflage patterns)
- Natural Selection
- The struggle for existence
- Variation
- The role of the environment
What is the struggle of existence?
There is a ‘struggle for existence’ amongst individuals of a population
- In most cases, only a small percentage of offspring survive every generation and go on to reproduce
- Ex. Pandas produce 2-3 offspring at a time, but only 1 survives due to limited milk production by the mother.
What is variation?
Variation: differences among members of the same species
- Sometimes a certain variation is best suited to a specific environment
- Individuals with this heritable variation are more likely to produce the most offspring
- This variation will become more common over many generations
What is the role of the environment?
The environment selects individuals in a species with variations that are best suited for that environment
What is fitness?
an individual’s ability to survive and reproduce in a specific environment
What is survival of the fittest?
individuals in a population with increased fitness will survive and reproduce the most successfully (Synonym for natural selection)
Natural selection does not make organisms ‘better’; an adaptation might work well in one environment but not so well in another
List all the Evidence for Evolution
- Fossil Records
- Geographic Distribution
- Comparative Anatomy of organisms
- Comparative development of species
- Molecular Biology
What are fossil records?
Definition: Chronological collection of life’s remains in rock layers, recorded throughout time
- Layers of sedimentary rock contain fossils
- A fossil is any preserved remains, impression, or trace of an organism from the past
- New layers cover older ones, creating a record over time
- Fossils within layers show that a succession of organisms have populated Earth throughout a long period of time
- What they can show
- Paleontologists rely on transitional fossils to show a possible link between two or more organisms
- Example: Fossil evidence supports the hypothesis that whales (which have no limbs) evolved from land-dwelling ancestors that had four limbs
- Fossil records can also provide evidence for the extinction of species
- Fossils records (and thus evolutionary history) are limited for species that do not possess bones, shells or exoskeletons
What is geographic distribution?
The differences and similarities between organisms in different parts of the world suggest that today’s organisms evolved from ancestral forms
- Organisms that are closely related but different:
- Ex: Finches on the Galapagos – all thought to be descended from a single ancestral species from South America.
- Organisms that are distantly related but similar:
- Idea that similar habitats (even if they are on opposite sides of the world) select for similar adaptations
- Ex: Sharks and dolphins have been hypothesized to have developed similar adaptations in spite of being very distantly related
What is comparative anatomy?
Homologous, analogous, vestigial structures
What are homologous structures?
structures that share a common origin/ancestry but may serve different functions in modern species
Ex: dolphin flippers and human hands
What are analogous structures?
features structures similar in function but not in origin or anatomical structure
Ex: wings of birds and bees, or the eyes of lobsters and fish
What are vestigial strucutres?
type of homologous structure that might have had a function in an ancestral species but no clear function in some of their modern descendants
- Usually smaller in modern descendants
- Natural selection would favour the survival and reproduction of individuals that possess reduced vestigial structures
What is Comparative Development?
Similar embryological development in closely related species.
- Embryos of closely related organisms often have similar stages of development.
- Example: All vertebrate embryos have gills and a tail in early development.
What is molecular biology?
- If two species have long sequences of DNA or proteins that match closely, these sequences were likely copied from a common ancestor
- All aerobic species contain the same protein required for cellular respiration: cytochrome C
- The greater the similarity in protein structure between two species, the more recent their common ancestry
What is artificial selection?
- Artificial selection: the selective breeding of domesticated plants and animals to produce offspring with genetic traits that humans value
- Allows for rapid changes in a species in short amount of time
- In this case, breeders do what the environment normally does in natural selection (ex. Breeding for dogs with certain characteristics)
What is antibiotic resistance?
- It was discovered that natural selection worked on the variations of the TB bacteria by selecting for the strains that were resistant to the antibiotics
- In general, it is important to fully complete a treatment of antibiotics prescribed by your doctor!!! If you do not, you are eliminating the ‘weaker’ bacteria, leaving more ‘fit’ bacteria to survive due to natural selection and allowing them to reproduce more!
- Natural selection is easy to observe in bacteria because their life cycles are so quick
What is microevloution?
A species population that is changing its genetic makeup over generations (and therefore evolving)
What is the gene pool?
Consists of all of the alleles in the individuals that make up a species population
- The ‘reservoir’ from which the next generation draws its genes
- Where genetic variation is stored
What are the two main sources of variation in the gene pool in a species population?
Mutation
Sexual Reproduction
What is a mutation?
- A change in the sequence of DNA
- Results because of mistakes in DNA replication (random) or exposure to chemicals/radiation
- Can improve, decrease, or have no effect on an organism’s fitness
What is sexual reproduction?
- Scrambling of existing alleles
- Meiosis (formation of eggs and sperm) and fertilization shuffle the alleles and recombine them (each offspring receives a new combination of alleles)
- Differences among individuals are largely the result of sexual recombination
What is the Hardy-Weinberg equilibrium?
Populations that do not undergo changes to their gene pool (and are therefore not evolving)
- Allele frequencies will stay the same across generations.
When will the Hardy-Weinberg equilibrium be maintained?
- Random Mating (no preference for particular genotypes)
- No immigration/emigration (no gene flow or individual/gametes entering or exiting a population)
- No mutations (no alleles/genes are altered)
- Very large population (infinite)
- No selection (all alleles/genes have equal fitness)
What are the mechanisms of micro-evolution?
- Natural Selection
- Sexual Selection
- Artificial Selection
- Genetic Drift
- Gene Flow
Name the different types of natural selection?
- Stabilizing
- Directional
- Disruptive
What is Stabilizing selection?
- Individuals with the most common variant of a trait are selected for (have higher fitness)
- Those that are very different from the average are selected against
- Results in the reduction of extreme values
What is directional selection?
- One extreme variant of a trait is favoured over the average variant
- Population tends to evolve towards that variant
What is disruptive selection?
- Selection favours two or more variants that are different from the average
- Individuals who have extreme variations of a trait have the highest fitness
What is sexual selection?
Features that have evolved because of sexual selection:
Lion with a big mane is selected by a female over a lion with a little mane. The genetic code is then passed onto male offspring
What is artificial selection?
- The selective breeding of domesticated plants and animals to produce offspring with genetic traits that humans value
- In this case, breeders do what the environment normally does in natural selection
What is genetic drift?
- Change in the allele frequencies of a population by random chance (unlike natural/artificial selection)
- Smaller the population, the more impact genetic drift has on it
What is the bottleneck effect?
- A sudden, drastic decrease in population size, often via natural disasters
- By chance, certain alleles may be represented more frequently than others (some might be eliminated altogether)
- Decreases genetic variation
What is the founder effect?
- A small group separates from the main population to colonize a new habitat
- The smaller the colony, the less its genetic makeup will represent the gene pool of the population it came from
- Decreases genetic variation
What is Gene Flow?
- Gene flow involves the movement of genes into or out of a population, due to either the movement of individual organisms or their gametes (eggs and sperm, e.g., through pollen dispersal by a plant)
- Random process (like genetic drift)
- Members of a species can interbreed
- Exchange of alleles with another population of the same species
- Reduces genetic differences between populations
Define Species.
individuals who can breed with one another in nature and whose offspring are fertile
What is allopatric speciation?
The formation of a new species as a result of evolutionary changes following a period of geographic isolation.
What is sympatric speciation?
The evolution of a populations within the same geographic area into separate species.
What are all the reproductive barriers?
- Geographic isolation
- Habitat isolation
- Temporal isolation
- Mechanical isolation
- Hybrid inviability or infertility
What is reproductive isolation?
Inability of two organisms to reproduce due to some kind of physical or behavioural barrier
What is geographic isolation?
- Geologic processes that change and rearrange Earth’s features can separate different populations of the same species and prevent them from reproducing
- Ex. Emergence of a mountain range
- Splintered populations may follow their own evolutionary courses and eventually may become separate species
What is habitat isolation?
- Individuals become reproductively isolated because they adapted to different types of habitats in the same general location
- Two (now) separate species’ preferences for different habitats help maintain their isolation
- Ex. Two species of garter snake exist because one lives mainly in the water while the other lives mainly on land; both species rarely interact
What is temporal isolation?
Species have different flowering or breeding seasons
Ex. Certain cacti species flower at night, others during the day
What is mechanical isolation?
Two seemingly similar species can’t mate because their reproductive structures are physically incompatible
Ex. Orchids are adapted to specific pollinators, preventing species cross pollination
What is Hybrid inviability?
Hybrid is born but dies early in development or early in life
What is hybrid infertility?
Hybrid offspring can mature into offspring but cannot reproduce
Ex. Mules (female horse and male donkey) are physically healthy but infertile
What are the Forms of Macroevolution?
- Convergent evolution
- Divergent Evolution
- Antagonistic Evolution
- Mutually beneficial co-evolution
What is gradualism equilibrium?
Accumulation of small genetic changes over a long period of time Change is gradual and continuous, resulting in transitional forms
What is punctuated equilibrium?
Relatively short periods of rapid change that result in the formation of new species Species remain in the same form for long periods of time
What is Adaptive Radiation/Divergent Evolution?
- the large scale evolution of a group into many different forms
- Evolution from a common ancestor that results in diverse species adapted to different environments (homologous structures)
- Often result from species colonizing remote islands, which are relatively isolated from major continents and contain diverse habitats
What is convergent evolution?
- The evolution of similiar traits in distantly related species
- Distantly related species that live in similar environments develop similar adaptations
- These traits are called analogous structures
What is co-evolution?
A process in which one species evolves in response to the evolution of another species
