2B - Evolution Flashcards
Chapter 4 - Mechanisms of a population change
What is an adaptation?
An adaptation is a physical feature,
behaviour, or physiological process that helps an organism survive and reproduce in a particular environment
What are the 3 different types of adaptations?
Structural/Physical
Physiological
Behavioural
Structural/Physical adaptation
changes in the structures of a living organism that makes it better adapted to its
environment
– Camouflage and colouration
– Morphological features such as changes in
the skeleton, limbs, tails, etc.
– Other physical characteristics of an organism
Behavioral adaptations
things an organism does to survive,
usually in response to an external
stimulus
– Nesting and hibernation behaviours
– Collecting and storing food, a food
cache
– Bird calls, songs, mating dances, and
migration
Physiological adaptations
- changes in the metabolism and / or physiological activity of organisms that allow them to maintain homeostasis
- These adaptations influence internal
functioning of the organism
– Breathing rate, temperature regulation in
endotherms, chemical mechanisms
– Odour production in skunks through secretory glands
– Digestive enzymes and the secretion of gastric acid
What is genetic variation?
- the difference in
DNA among individuals or the differences
between populations among the same
species - The multiple sources of genetic variation
include mutation and genetic
recombination
– Mutations are the ultimate sources of
genetic variation, but other mechanisms,
such as genetic drift, contribute to it, as well
What is genetic variation caused by
Genetic variation is caused by variation in
the order of bases in the nucleotides in
genes
What will genetic variation will result in
phenotypic variation if the order of nucleotides in the DNA sequence results in amino acid changes
– Amino acid changes can result in new proteins coded by that DNA sequence
– If resultant differences in amino-acid sequence influence protein shape, it can change function
What is phenotypic
variation?
Differences within the observable characteristics among an individual/s within a population.
What is variety and what can it cause
/
Variety (in the phenotypic expression of
organisms) within a population exists
- This variation within a particular environment can result in an organism being better or less adapted to their particular situation
- Thus, phenotypic variation is the
characteristics on which natural selection acts
Natural selection
Natural selection is the process by which a population of organisms changes because individuals with certain traits can better survive the local environmental conditions and pass on these traits to their offspring.
What is a genetic mutation?
- Changes in the DNA sequence of genes
can result in the production of new
proteins - Mutations can be:
– Benign (have no effect on the organism)
– Deleterious (harmful to the organism)
– Advantageous (helpful to the organism)
What is a phenotype
observable characteristics due to thier genes and environment. a difference in phenotype causes variation among a species
What do genes code for
proteins/amino acids
what do genomes code for
genomes are all your genes combined and they code for the entire organism
what are phenotypes the result of
Phenotypes are the result of the genetic
sequence / code and the influence of
environmental factors on gene expression
What are selective pressures?
Variable which cause a certain phenotype of an organism to have a better chance at survival
- Organisms possessing a particular characteristic are either eliminated or favoured by an environment
- Selective pressures reduce or increase reproductive success of organisms, which drives natural selection
“Fitness”
- Does not mean survival of the fittest
- it is the ability of an organism to survive and reproduce
- a measure of the average contribution to the gene pool of the next generation of an organism with particular genotype/phenotype
Darwins theory of evolution
- Evolution occurs as organisms change over time
- Descentants diverge from common ancestors in the past
- Evolution occurs by natural selection
- Process in which living things with beneficial traits produce more offspring than others do. This results in changes in the traits of living things over time
(gets more common over time)
- Process in which living things with beneficial traits produce more offspring than others do. This results in changes in the traits of living things over time
Are environments changing or static
Environments are not static, they change
- Gnetic makeup
- Phenotypes
Like adaptations, mutations all that stuff
Heritable traits
Traits or characteristics that can be passed on from parent to child
Genetic
Acquired trait
Not heritable
It’s something someone learns in their life and is not genetic
Jean Baptiste Lamarck
- “Law of Use and Disuse” = Use it or lose it
Ind. lose traits their env. doesn’t need and gains traits they need to survive - Thought aquired traits can be passed down
What are the scientific evidences for evolution
- direct observation
- fossil record
- biogeography
- Anatomy, homology and convergent evolution
- Molecular biology and genetics
Direct observation
- We can actively see it happening around us
ex: bacteria becoming resistant to parasites and vaccines
Fossil record
– Fossils are remains or traces of organisms from the past found in sedimentary rock.
– Radioactive dating is used to determine the age of fossils and geological principles such as the Law of Superposition.
– Darwin’s theory of evolution through natural selection explains the succession of forms in the fossil record.
– Transitional fossils have been found that link ancient organisms to modern species, as Darwin predicted.
Embryonic Homology
- comparison of early stages of animal dev. reveals many anatomical homologies (morphological similarities) in embryos not visible as an adult
Molecular homologies
- shared characteristics on the molecular level
- All life forms ise the same genetic language of DNA and RNA
- when hox genes are tampered with, legs can replace antennae etc
Transitional fossils
- any fossil that possesses characteristics of both ancestral and decsendant groups
- show the progression of the dev. of new evo. traits and display the loss of other traits over time
Definition of homology
- characteristic in related species can have an underlying similarity even with very different functions
Homologous structures
anatomical eviddence for evolution
- occurs in species that have a common ancestor
- similar functions, although they may have different physical appearences.
analogous structures
- perform similair functions but organisms dont have a common ancestor/ evolutionary origin
- no evidence of a common ancestor
- insect wing vs bat wing
Vestigial organs
- structures of minimal importance to the organism
- remnants of structures that served important functions in the organisms ancestors
Convergent evolution
- taken place when two organisms developed similarities as they adapted to similar environmental challenges
- not because they evolved from a common ancestor
- similar problem = similar solution
divergent evolution
accumullation of differences between closely relates populations within a species, sometimes leading to speciation
Biogeography
- geographic distribution of a species
- species in discrete geographic area tend to be more closely related to each other than to species than to species somewhere else
Adaptive radiation
the diversification of a group of organisms into forms filling different ecological niches.
think of darwins finches on galapalos
Introduced vs invasive
An introduced species is one that is moved into a new area that it is not naturally found in. An invasive species is an introduced species that disrupts natural ecosystems.
may become invasive if environmental pressures are diff in new env. breeding more without a natural predator
