Honors Bio: Unit 8
Introduction
DNA → RNA → Protein → Traits
DNA→ Mutation →leads to new trait
Dna is the raw material necessary for evolution to occur (cause changes)
How do organisms evolve?
We are trying to figure out how organisms change over time until they end up as distinct species.
What is a species?
Means specific
Similar characteristics
They can breed together, and need the right amount of chromosomes
Exp. horse + donkey mate - mule
What does the term evolution mean?
Adapting and changing over a long period of time (not in an organism lifespan)
A species evolves, not one organism
Organism does not know they're evolving, not a conscious change, it just happens
Happens because of: genetic diversity + environmental change ⇒ drives evolution
How do you think organisms evolve?
Random mutations within an organism
Cross-breeding
Death of organism that couldn’t survive in the current environment
Environmental change + adaption
Survival of the fittest meaning?
organisms best adjusted to their environment are the most successful in surviving and reproducing.
Who is BEST adapted to the environment
Evidence of Evolution
We need to use some criteria to determine whether evolution has occurred, we use:
Five Main Categories
Anatomy- Species may share similar physical features because the feature was present in a common ancestor (homologous structures).
Molecular biology- DNA and the genetic code reflect the shared ancestry of life.
DNA comparisons can show how related species are.
Biogeography- The global distribution of organisms and the unique features of island species reflect evolution and geological change.
Fossils-Fossils document the existence of now-extinct past species that are related to present-day species.
Direct observation- We can directly observe small-scale evolution in organisms with short life cycles (e.g., pesticide-resistant insects). ⇒ exp bacteria
Anatomy and Embryology
Bones in the appendages of a human, dog, bird, and whale: all share the same overall construction.
Results from origin in the appendages of a common ancestor
Over time: evolution led to changes in the shapes and sizes of these bones in different species,
BUT they have maintained the same overall layout -- evidence of descent from a common ancestor.
Homologous Structures is what Scientists call these
Analogous Structures exp ⇒
They are all wings, (share the same function), however, bats r more related to humans
Vestigial Structures =
unused structures without function
appear to be residual parts from a past ancestor
Exp. snakes have pelvic bones, even tho they don't have legs
Because they descended from ancestor that DID have legs
Humans = wisdom teeth from chimps
Molecular Biology
Like anatomical structures, the structures of the molecules of life reflect descent with modification.
Evidence of common ancestor: reflected from universality of DNA
DNA replication + expression
Relatedness of groups of organisms reflected: similarity of their DNA sequences
exactly the pattern that would be expected from descent and diversification from a common ancestor
Biogeography
Geographic distribution of organisms on the planet follows patterns that are best explained by evolution in conjunction ⇒ with the movement of tectonic plates over geological time
Breakup of supercontinent: Pangaea
After two super continents broke up, groups were distributed accordingly
Australia, the Galapagos, and Hawaii: have long had species unique to them
typical of islands ⇒ isolated by water prevents migration of species to other regions
Over times, species become unique ⇒ look different from ancestors
Fossils
provide solid evidence that organisms from the past are not the same as those found today
show the gradual evolutionary changes over time
Scientists determine age of fossils from:
radioactive dating
Categorize them over world to see relative location
Direct Observation
we can see evolution occurring right before our eyes
Exp. Superbugs
are bacteria that are super resistant to antibiotics
can evolve under the right conditions in a matter of days
Mechanism of Antibiotics:
Basctial static
Prevent growth of bacteria
Bastical cyto
Antibiotic = drug, used to treat bacterial infections
Leave human cells alone (penicillin)
The way they affect bacteria can vary
Some prevent cell wall from growing
Putting into environment that is hypertonic ⇒ cell explode
Bacteria can fight back!
4 things that MUST be true for natural selection to occur:
Variation in Population
Every species has variations
Sexaul = genes
Asxeual = mutations
Happens between related individuals
Variation is good if not EXTINCTION, cannot adapt to changing environment
Inherited Traits
Have to be born w variations
Traits passed from parents to offspring determine the characteristics of the offspring
Inherited traits that improve the odd of survival are more likely to be passed to on to subsequent generations.
Trait has to be present for natural selection to occur
Offspring Compete
Most species produce more offspring each year than the environment can support.
High birth rate results in competition among the members of the species for the limited natural resources available
Struggle for resources: determine mortality rate within a species
Only surviving individual breeding pass on their genes to the NEXT generation
Survival of the Fittest (or natural selection)
Need specific traits to survival, selective advantage
Traits that helped these organisms survive will be passed on the their: natural selection
Types of Natural Selection:
Selective pressures are extreme agents which affect an organism ability to survive in a sigve environment
Can be negative
Types:
-resource availability (presence of food, habitat, mates)
-environmental condition (temp, weather, geographical access)
-biological factors (predators/pathogens)
Three Roles of selective pressure:
Direction selections: select one trait over another, shift genetic variation in one way (more pop has one)
Selective pressure = predators
Stabilizing selection: selects for a trait in between two extremes
Human birth weight
Disruptive selection:
Selects for both extreme traits
Ultimately leads to the formation of new species
Two distinct traits
Superbugs: directional selection
Types of Evolution:
Divergent Evolution:
One species diverge in traits and become two distinct species
Usually a result of geographic isolation
Wooly mammoth + elephant = common ancestor, changed because of climates
Convergent Evolution:
Two organism evolve similar characteristic do not share a common ancestor
Usually the result of organisms developing in similar environments
Analogous sturctions
Coevolution
Symbotic relation evolve characteris that coincide with that relationship
Bird + butterfly
Punctuated Equilibrium
Rapid change in a spcieces takes place in short burst rather than in a gradual change
Macroevolution vs. Microevolution (04/29)
Microevolution: Within the species ⇒ Not a large change, thus staying within the same species
Anagenetic Change: Changes to the allele frequency
Light Moths evolve from Dark Moths due to the environment
The dark moths have a larger chance of survival due to Industrial Revolution
The Clean Air Pact passes and the light moths become prevalent
Macroevolution: Ultimately when the variations accumulate to the point where a new species forms. (Clade Evolution)
There has to be some sort of isolation in order for macro to exist
Takes a long time
Needs to be within a large population -- like the dinosaurs
Macroevolution (04/30)
Macroevolution can only occur if microevolution happens first
There has to be some sort of isolation in order for macroevolution to occur:
Geographical Isolation: Part of the species has been geographically separated and can evolve into its own species
Temporal Isolation: Populations within species that breed in different places/at different times slowly become different species
Behavioral Isolation: Different species have different ways of attracting a mate ⇒ Dances, sounds, colors, etc. Each species has a unique behavior for mating.