Bio test (Evolution) Flashcards
The Theory of Evolution
an explanation of how species change over time. this theory suggests that modern species are the result of past changes in genes which were passed down to generations.
extinction
mass extinctions decrease the number of species
adaptation
Due to gradual, accumalative changes that help organisms survive and reproduce. Adaptations are caused by random genetic mutations in DNA.
selective advantage
A genetic advantage that improves an organism’s chance of survival in a changing environment
When an organism has selective advantage, that organism is going to survive and reproduce
Obvious at birth
A mutation can quickly spread in populations because of selective advantage, since bacteria and viruses can reproduce quickly.
Structural adaptation
Physical features of an organism
Examples:
Beak variety on birds
camouflage
Mimicry
behavioural adaptation
Things organisms do to survive.
Examples:
Migrating to a new area
Mating calls
physiological adaptation
Changes or chemical reactions that occur within an organism
examples:
venom
Hibernation (surviving in harsh conditions by keeping warm and preserving energy)
what is a scientific law?
a statement based on repeated experiments observations
What is a scientific theory?
an explanation that has been aquired through the scientific method and repeatedly tested and confirmed through observation and experiments
Survival of the fittest
Fitness: the contribution an individual makes so that its offspring can survive longer and has offspring of its own
Changes that limit survival:
Severe weather
Famine
Disease
Competition for food, space, mates, etc.
The organisms that survive these conditions pass their genes to the next generation, which is why they are called the fittest genes.
If an organism is healthy and survives for a long time, it has offspring that also has its traits, which means it can also survive longer. This shows how that organism is the fittest.
Jean-Baptiste Lamarck
He believed that over the time of their lives, organisms adapt to their environment better, as they strive for perfection. He introduces the idea of inheritance of acquired characteristics, meaning that once a organism “perfected” its traits and skills, it will pass that same skill to its offspring
Charles Darwin
Proposed the idea of the theory of natural selection, where life changes and continues to change based on natural pressures. he used the survival of the fittest to develop this theory.
Natural selection
The process of where characteristics of a population changes over time, and generations that have heritable traits survive for longer periods of times, passing their traits to their offspring.
Selective pressure
Environmental conditions select for certain characteristics of individuals and select against others.
Examples:
temperature change
Change in pressure
Change in competitions
Forms of selective pressure:
Biotic and abiotic factors
Biotic factors
A living component that affects another organism
Examples: parasites, predators, competition
Abiotic factors
Changes in the environment that alter the behaviour in a population
Examples: weather, pesticides, urban vs. rural, antibiotics
Artificial selection
Selective pressure exerted by humans on populations to improve or modify desirable traits.
Examples:
cats and dogs are bred for appearance
Cows are bred for more muscle in meat
Chickens are bred to produce more eggs
Reasons why farmers do artificial selection:
increase nutritional value
increase production and the economy for countries dependent on crops
To be drought-resistant and pest-resistant
Consequences:
inherited traits can cause severe side effects
Monoculture: only one type of crop is grown in the same place at the time time, producing identical plants. This reduces genetic diversity which is bad since if theres a disease that inflects a crop, it will affect all of them.
weak soil
more fertilizer
spread of pests
spread of diseases
more pesticides
Positive consequences:
growing requirements
maintenance
pest control
standardized harvesting
Greater yield
gene banks: contains seeds from early ancestors, which are used to modern seeds if it’s needed since they survive for a long time. its goal is to preserve genetic diversity
How was evolution proven?
the fossil record
biogeography
anatomy
Embryology
DNA
The fossil record
Specific fossils are found within specific layers
(strata) of sedimentary rock
Paleontologists use this to determine dates
The youngest fossils (similar to species alive today) are found closest to the surface and the oldest fossils are found deeper.
Not all organisms appear in the fossil record at the same time
Transitional fossils are always being researched and found to fill in the space between the past and the present, where some organisms developed differently.
Vestigial structure
reduces versions of what was once functional structures in an ancestral species
Biogeography
The study of the geographical distribution of species
○ Geographically close environments are more likely to have related species
○ Animals found on islands closely resemble animals on the nearest continent
○ Fossils of the same species can be found on the coastline of neighbouring continents
Anatomy
Homologous Structures
● Structures that have similar structural elements and origin
● May have a different function
● Originate from a common ancestor
○ Example: hair on mammals
Analogous Structures
● Structures that do not have a common evolutionary origin
● Perform similar functions
● Provide evidence for adaptations to suit the environment
○ Fins on a dolphin vs. fins on a fish
Embryology
The study of prebirth stages of an organism’s development
This helps us to see evolutionary ancestors between organisms
DNA
comparing genetic sequences can help determine similarity
Two organisms with similar DNA suggests that they inherited these traits from a common ancestor
How is each generation different/unique?
independent assortment
crossing over
new random mutations leading to new traits
Genetic variation is random but natural selection isn’t random because fit genes will survive and reproduce
Gene pool
A population that consists of all alleles of all genes of each generation.
Allele frequency
The number of copies of an allele compared to the total number of alleles in a population
Factors that affect allele frequency:
mutation - change in the DNA of one individual. A heritable mutation (gamete) may affect an entire gene pool
gene flow (migration) - the net movement of alleles from one population to another due to the migration of individuals
Non-random mating - mating among individuals on the basis of a particular phenotype. Inbreeding is another example
Genetic drift - The change of frequencies in alleles due to chance events in a population.
natural selection (most significant) - selective forces affect populations. Theres 4 types of natural selection (stabilizing, directional, disruptive, sex)
More genetic variation in a population = greater diversity = greater chance of selective advantage in a changing environment
Microevolution
The change in % of frequency of alleles within a population
Can lead to evolution
The founder effect
A new population started by a few members of the original population. The new founders carry most alleles from the original population to the new population.
reduces genetic variation
The bottleneck effect
When a population is quickly reduced (from starvation, disaster, etc.) and the surviving organisms start a new population
Stabilizing selection
favors intermediate phenotypes and acts against extreme variations of the phenotype
Directional selection
favours phenotypes at one extreme over the other (especially in environmental change)
Disruptive selection
favours the extremes of a range of phenotypes which can cause the intermediate to be eliminated
Sex selection
competition for mates between males through combat or physical appearance
Macroevolution
The formation of a new species from an existing species
Allopatric speciation
population are seperated by a geographical barrier. gene flow is interruped,
Adaptive radiation
diversification of a common ancestral species into a variety of differently adapted species
Sympatric speciation
populations in the same geographical area become reproductively isolated (common in plants since they can’t move)
Prezygotic isolating mechanisms
eggs cannot be fertilized
Behavioral: species have a specific signal or behaviour that prevents inbreeding (birds have different songs)
Habitat: two species live in the same area but different habitats and do not interact (water vs. open land)
Temporal: some species reproductive organs are incompatible and unable to fertilize
Gametic: a species gametes are not able to fuse to form a zygote (example: sperm cannot survive in the female reproductive tract)
Postzygotic isolating mechanisms
Sperm and egg meet but zygote cannot develop into a viable egg
Hybrid inviability: when genetic information is not compatible between species (zygote doesn’t undergo mitosis and cannot develop)
Hybrid sterility: two species can mate but the hybrid is sterile, meaning meiosis fails to produce “normal” gametes (example: horse and donkey create mule, which cannot have offspring)
Hybrid breakdown: two organisms are able to mate and produce viable and fertile offspring, but when the offspring mate (second generation inbreeding), their offspring will be weak
Convergent evolution
similar traits arise because different species independently adapted to similar environmental conditions (example: birds and bats both have wings, but they don’t have a common ancestor)
The speed of evolutionary change
Gradualism: views evolutionary change as slow and steady (before and after divergence)
Punctuated Equilibrium: views evolutionary history as long periods of equilibrium that are interrupted by periods of divergence
Some species show a gradual change over a period of time while others evolve quickly during the periods of history
Divergent evolution
species similar to the ancestral species diverge and become distinct due to changing environmental conditions (example: birds have a common ancestor but they have different types of beaks based on their diet)
