evolution Flashcards
Extinct
Describes a species that has completely disappeared from earth
Adaptation
A structure, behaviour, or physiological process that helps an organism survive and reproduce in a particular environment
Mimicry
A structural adaptation in which a harmless species resembles a harmful species in coloration or structure
Variation
Differences between individuals, which may be structural, functional, or physiological
Mutation
A permanent change in the genetic material of an organism; the only source of new genetic variation
Selective advantage
A genetic advantage that improves an organism’s chance of survival, usually in a changing environment
Natural selection
The process by which characteristics of a population change over many generations as organisms with heritable traits survive and reproduce, passing their traits to offspring
Selective pressure
Environmental conditions that select for certain characteristics of individuals and select against other characteristics
fitness
the relative contribution an individual makes to the next generation by producing offspring that will survive long enough to reproduce
artificial selection
selective pressure exerted by humans on populations in order to improve or modify particular desirable traits
biotechnology
the use of technology and organisms to produce useful products
monoculture
extensive plantings of the same varieties of a species over large expanses of land
paleontology
the study of ancient life though the examination of fossils
catastrophism
the idea that catastrophes such as floods, diseases, and droughts periodically destroyed species living in a particular region, allowing species from neighbouring regions to repopulate the area
limited to local geographical regions, and the area would be repopulated by spaces from nearby unaffected areas.m how he explained the appearance of fossils that no longer existed anymore.
uniformitarianism
Charles Lyell’s theory (based on Hutton’s theory) that geological processes operated at the same rates in the past as they do today
inheritance of acquired characteristics
the idea that characteristics acquired during an organism’s lifetime can be passed on to its offspring
theory of evolution by natural selection
a theory explaining how life has changed during earth’s history
evolution
the process of genetic change in a population over time
Survival of the fittest
The idea that the organisms that are the fittest leave the most offspring,so those organisms win the struggle for survival; phrase coined by john Spencer
Descent with modification
Darwin’s theory that natural selection dose not demonstrate progress, but merely results from a species’ ability to survive local conditions at a specific time
Fossil record
The remains and traces of past life that are found in sedimentary rock; it reveals the history of life on earth and kinds of organisms that were alive in the past
what type of rock shows ghistory of life?
sedimentary
evidence form the fossil record (5)
- Fossils found in young layers of rock are much more similar to species alive today than fossils found in older, deeper layers of rock.
- Fossils appear in chronological order in the rock layers. So, probable ancestors for a species are found in older rocks, which usually lie beneath the rock in which the later species is found.
- Not all organisms appear in the fossil record at the same time
- oldest birth is archaeopteryx (intermediate between bird and dinosaur)
- in darwins time used relative dating
relative dating
position of the fossil in the sediment gives general relationship
absolute dating
actual age of fossils estimated by reates of radioactive decay
Transitional fossil
A fossil that shows intermediary links between groups of organisms and shares characteristics common to two now separate groups
Vestigial structure
- A structure that is a reduced version of a structure that was functional in the organism’s ancestors
- no apparent function but resemble structures their ancestors possessed
e.g humans: muscles for wiggling ears
manatees: fingernails on their fins
bind cave fish: nonfunctional eyes
Biogeography
The study of the past and present geographical distribution of species populations
evidence from bio geography (4)
- Geographically close environments (for example, desert and forest habitats in South America) are more likely to be populated by related species than are locations that are geographically separate but environmentally similar (for example, a desert in Africa and a desert in Australia)
- Fossils of the same species can be found on the coastline of neighbouring continents
- Animals found on islands of en closely resemble animals found on the closest continent. This suggests that animals
on islands have evolved from mainland migrants - Closely related species are almost never found in exactly the same location or habitat.
evidence from anatomy (homo)
Homologous structures are those that have similar structural elements and origin but may have a different function
Homologous structures are similar because they were inherited from a common ancestor. can be similar in structure, function, or both
Homologous structures
- structure with different appearances and functions that all derived from the same body part in a common ancestor
- differing functions, same ancestor and structure
Analogous structures
- structure (‘adaptations’) with same type of use or function that are not fundamentally similar in structure
- implies two organism did NOT have a common ancestor
-
same function, different ancestral structure
e.g wings of a beetle, and wings of a bird - acts as evidence of the process of convergent evolution
evidence from embroyology (3)
- Embryology studies early, pre-birth stages of an organism’s development.
- Embryology has also been used to determine evolutionary relationships between animals.
- The embryos of different organisms exhibit similar stages of embryonic development.
evidence from dna
Since DNA carries genetic information, scientists can determine how closely related two organisms are by comparing their DNA. If two species have similar patterns in their DNA, this indicates that these DNA sequences must have been
inherited from a common ancestor.
Current evolutionary theory connects genetics with the theory of natural selection,
and how natural selection operates on populations
Embryology
The study of early, pre-birth stages of an organism’s development
Gene flow
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 mate selection for a particular phenotype or due to inbreeding
Genetic drift
The change in frequencies of alleles due to chance events in a breeding population
The founder effect
A change in a gene pool that occurs when a few individuals start a new isolated population
- often new populations are formed by only a few individuals or founders
- the founders will carry some, but not all, of the alleles from the original population’s gene pool, therefore the diversity in the new gene pool will be limited
- frequently occurs on islands, and probably happened when various plants, insects, birds, and reptiles first colonized the Hawaiian and Galapagos Islands
- happens in human populations too, the incidence of inherited health conditions in these populations is much higher than average
Bottleneck effect
Changes in gene distribution that result from a rapid decrease in population size
- starvation, disease, human activities, and natural disasters
- since survivors likely have only a fraction of the alleles that were present before the population decline, the gene pool has lost diversity
- genetic diversity is very low
EXAMPLE: fewer than 30 survivors from a typhoon in Pingelap, and one of the survivors carried a genetic mutation that causes colour vision deficiency. now about 10% of the population of the island has colour vision deficiency, though world wide the codinon is rare
Stabilizing selection
Natural selection that favours intermediate phenotypes and acts against extreme variants
- this type of selection reduces variation and improves the adaptation of the population to aspects of the environment that remain fairly constant
Directional selection
Natural selection that favours the phenotypes at one extreme over another, resulting in the distribution curve of phenotypes shifting in the direction of that extreme
- this type of selection is common during times of environmental change or when a population migrate to a new habitat that has different environmental condition and niches to exploit
Example: peppered moths
Disruptive (diversifying) selection
Natural selection that favours the extremes of a range of phenotypes rather than intermediate phenotypes; this type of selection can result in the elimination of intermediate phenotypes
- as a result, intermediate phenotypes can be eliminated from the population
example: mature male coho salmon, small phenotype os about 500g while the much larger may be 4500g
smaller salmon are specialized for “sneaking” opportunities to fertilize the eggs of females
larger salmon are better equipped for fighting for the same access to the female’s eggs
Sexual selection
Natural selection for mating based, in general, on competition between males and choices made by females
- involves competition between males through combat or through visual displays (showy feathers)
- involves the choices females make for mates
- the different characteristics as well as courtship displays and other mating behaviours, are also aspects of sexual selection
Speciation
The formation of new species from existing species
Pre-zygotic isolating mechanism
A barrier that either impedes mating between species or prevents fertilization of eggs if individuals from different species attempt to mate; also called pre-fertilization barrier
Post-zygotic isolating mechanism
the sperm of one species successfully fertilizes an egg of another species and a zygote is produced
A barrier that prevents hybrid zygotes from developing into viable,fertile individuals; also called post-fertilization barrier
Sympatric speciation
Spection in which populations within the same geographical areas diverge and become reproductively isolated
Allopatric speciation
Specification in which a population is split into two or more isolated groups by a graphical barrier; also called geographical speciation
Ecological niche
Ecological role and physical distribution of a species in its environment
Adaptive radiation
The diversification of a common ancestral species into a variety of differently adapted species
Gradualism
A model of evolution that these evolutionary change as slow and steady, before and after a divergence
Punctuated equilibrium
A model of evolution that these views evolutionary history as long periods of stasis, or equilibrium, that are interrupted by periods of divergence
theory of natural selection (5 points)
- Charles Darwin, Alfred Wallace (1858)
- Individuals with traits that helped them survive were more likely to pass these traits onto the next generation
- With each successive generation, the proportion of individuals with these traits would increase
- The population evolves, not the individuals, over a long time period and many generations
- In modern terms, this means that the frequency of certain alleles increases within a gene pool
Georges-Lewis Leclerc, Comte de
Buffon (1707-1788) (4)
- Noted similarities between humans and apes and the possibility of a common ancestor (Histoire Naturelle, 1769)
- Earth had to be older than 6000 years
- He was unable to explain how species change over
time - Challenged accepted dogma of the time
Mary Anning (1799-1847) (4)
- Family collected fossils in their hometown in southern England for income
- Developed a vast knowledge of fossils
- Helped discover the first specimens of an ichthyosaur and plesiosaur
- Her findings, contributions and knowledge were belittled
because she was not formally educated and a female
Georges Cuvier (1769-1832) (5)
- Founded vertebrate paleontology
- Confirmed Anning’s fossils as genuine
- Didn’t believe that lifeforms could evolve
- Established extinction as a fact
- Explained extinctions with “revolutions” or major destructive
natural events that wiped out species (catastrophism)
Charles Lyell (1797-1875) (3)
- Rejected catastrophism
- Built on ideas of Hutton (geologist)
- Theory of uniformitarianism
Jean Baptiste Lamarck
(1744-1829) (4)
- A botanist and expert in ivertebrates and classification
- Species do change over time. His explanation…
- Based on an analysis of an expanding fossil collection
- When environments changed, they “needed” to change to
adapt
Darwins (1809-1882) observations on the Galápagos islands (9)
- Species on a continent were distinct from those found on other continents
- Fossils from extinct animals looked similar to living animals
- The birds observed on the Galapagos Islands closely resembled those on the west coast of South America
- Finches on the Galapagos had different beaks depending on the food they ate
- Sexual reproduction within a species can produce offspring with inherited traits and in different variations
- Theory of Evolution by Natural Selection (Darwin “&” Wallace)
- Organisms produce more offspring than the environment can support (carrying capacity)
- Population sizes would eventually decrease due to density dependent factors such as food supply and disease
- Evidence favoured evolution (descent with modification) of all species from a common ancestor
What is Biological evolution
infers that certain similarities between species are evidence the two groups at one point may have shared a common ancestor
fossils
- fossils are the preserved remains of once-living organisms
rock fossils are created when three events occur: - organisms buried in sediment
- calcium in bone or other hard tissue mineralizes
- surrounding sediment hardens to from rock
- shows evidence of extinction
structural adaptation
how the animal’s body functions or looks on the outside.
embryo
an organisms early pre-birth stage of development
biochemistry
the application of chemistry to the study of biological processes at the cellular and molecular level
marsupial
young are born in a immature condition and held in a pouch until they develop
e.g koalas, opossums, wombats
placentals
young are not born until they can safely survive in the external environment
e.g humans, dogs, bears
convergent evolution
the independent development of similar structure in organisms that are not directly related
comparative embryology
strongest anatomical evidence supporting evolution comes from ea comparison of how organisms develop
- early vertebrate embryos possess pharyngeal pouches the develop into
- in humans: glands and ducts
- in fish: gill slits
MODIFICATION By NATURAL SELECTION
- gives a mechanism for how evolution can occur; environment limits the growth of populations by increasing the rate of death or decreasing the rate of reproduction, or both
- Organisms with greater number of favourable traits for that particular environment will leave more offspring (Different degrees of successful reproduction is natural selection)
- If a trait both increases the reproductive success of an organism AND is inherited, then that trait
will be passed on to many offspring - The population adapts over generations as proportion of genes for favorable traits increases
- Resulting change is evolution
- Organisms DO NOT purposefully acquire traits that they need
- The environment ‘selects’ the traits that will increase over several generations
- A favorable trait for the particular environment gives an organism an adaptive advantage
- If environmental change occurs too rapidly, adaptations cannot occur fast enough
something important to remember!
Individuals have adaptations
But individuals do NOT adapt
Lamarck vs. Darwin
- Use and disuse
- Transmission of acquired traits
- Increasing complexity
- No extinction
Vs.
- Variation in population
- Inheritance of traits
- Differential survival
- Extinction
Evidence of Natural Selection (2)
- When the environment changes, natural selection often favors different traits in a species
- When environmental conditions reverse, so does selective pressure
Industrial melanism:
phenomenon in which darker individuals come to predominate over lighter ones
Biston betularia: peppered moth
- Light gray with black specks to jet black coloration
- Black individuals have the dominant allele
- Dominant allele was rare in the population until 1850s
- Light moths were easily seen by birds on darkened (sooty) trees
Dark tree trunks
= more dark-colored moths survived
Light tree trunks
= more light-colored moths survived
3 conditions of natural selection
- Variation must exist in the population
- This variation must lead to differences among individuals in reproductive success
- Variation among individuals must be genetically transmitted to the next generation
speciation
the formation of new species from existing species
behavioural isolating mechanisms
Any special signals or behaviours that are species specific prevent interbreeding with closely related species.
example: eastern meadowlark and the western meadowlark These species are nearly identical in shape, coloration, and habitat, and their habitat ranges overlap. In the area where the ranges overlap, very little mating takes place between the two species, largely due to the differences in their songs.
Temporal Isolating Mechanisms
Many species are kept separate by temporal (timing) barriers.
example: example, two species may occupy the same habitat but mate or flower at different times of day, in different seasons, or in different years.
The species remain reproductively isolated despite living in the same habitat.
Mechanical Isolating Mechanisms
Species that are closely related may attempt to mate but fail to achieve fertilization because they are anatomically incompatible.
example: the genitals of some insects operate in a kind of lock-and-key system. If a male and female of different species attempt to breed, their genitals will not fit together.
Gametic Isolating Mechanisms
If gametes (egg and sperm) from diff erent species do meet, gametic isolation ensures they will rarely fuse to form a zygote.
example: in species in which the eggs are fertilized within the female reproductive tract, the sperm of one species may not be able to survive in the environment of the female reproductive tract of another species.
Hybrid Inviability
Genetic incompatibility of the interbred species may stop development of the hybrid zygote during its development. Hybrid inviability is usually due to genetic incompatibility, which prevents normal mitosis aft er fusion of the nuclei in the gametes.
example: hybrid embryos between sheep and goats
die in early development before birth.
Hybrid Sterility
However, a reproductive barrier still exists between the two species if the hybrid offspring is sterile.
Hybrid Breakdown
However, when these hybrids mate with each other or with an individual from either parent species, the offspring of the next generation are either sterile or weak.
gradualism
In modern biology, gradualism, or “phyletic gradualism,” refers primarily to a pattern of sustained, directional, and incremental evolutionary change over a long period during the history of a species.
SLOW PERIODICAL CHANGE
Phenotype
refers to an individual’s observable traits, such as height, eye color and blood type.
