Lecture Exam 1 Flashcards
the 8 general properties of living systems
- chemical uniqueness
- complexity and hierarchical organization
- reproduction
- possession of genetic program
- metabolism
- development
- environmental interaction
- movement
General property 1: chemical uniqueness
living systems demonstrate a unique and complex molecular organization
-small molecules assembled into macromolecules
(nucleic acids, proteins, carbohydrates, lipids)
General property 2: complexity
- living systems demonstrate a unique and complex hierarchical organization
- in living systems there exists a hierarchy of levels (macromolecules, cells, organisms, populations, species)
General property 3: reproduction
reproduction is a component of the definition of life
- at each level of the biological hierarchy, living forms reproduce to generate others like themselves
1. genes replicate to produce new genes
2. cells divide producing new cells
3. organisms reproduce to produce new organisms
4. populations fragment to produce new populations
5. species split to produce new species
general property 4: genetic program
genetic program provides fidelity of inheritance
- nucleic acids: encode the structures of the protein molecules needed for organismal development and functioning
- DNA: long, linear chain of nucleotides (stores genetic info)
- genetic code: correspondence between base sequences in DNA and the sequence of amino acids in a protein
general property 5: metabolism
living organisms maintain themselves by acquiring nutrients from their environments
- metabolic processes:
1. digestion (catabolic or anabolic)
2. energy production (respiration)
3. synthesis of molecules and structures required by organisms
general property 6: development
all organisms pass through a characteristic life cycle
-development describes the characteristic changes that an organism undergoes from is origin to its final adult form (ex. caterpillar -butterfly)
general property 7: environmental interaction
all animals interact /w their environment
- Ecology: study of organismal interaction /w an environment
- all organisms respond to environmental stimuli, a property called irritability
general property 8: movement
living systems and their parts show precise and controlled movements arising from within the system
-living systems extract energy from their environments permitting the initiation of controlled movements
what is the meaning of “the living world is neither constant nor perpetually cycling, but is always changing”
- the varying forms of organisms undergo measurable changes across generations throughout time
- documented by the fossil record
- theory upon which the remaining four are based
(analogy: you will never step into the same river twice) - the water isn’t the same, you aren’t the same and the organisms living inside the river aren’t the same
adaption
an anatomical structure, physiological process or behavioral trait that evolved by natural selection and improves an organisms ability to survive and leave descendants
adaptive radiation
the evolution of several ecologically diverse species from a common ancestral species within a short geological time interval
- new lakes and islands provide new opportunities for organisms to settle and evolve
- early settlers who were under heavy competition before are now free to colonize the new habitat
- geographic isolation leads to more speciation
homology
Darwin saw this as major evidence for common descent
- richard owen described this as “the same organ in different organisms under every variety of form and function”
- vertebrate limbs show the same basic structures modified for different functions
- every time a new feature arises on an evolving lineage, a new homology forms
- homology gets transmitted to all descendant lineages unless it is subsequently lost
radiometric dating
methods:
- potassium argon dating
- potassium 40 decays to argon 40 an calcium 40
- half life of potassium 40 is 1.3 billion years
- calculating the ratio of remaining potassium 40 to amount originally there provides close mathematical estimate of the age of rock deposit
- rate of decay of uranium into lead
- one of the most useful radioactive clocks
- can date age of earth
- error is less than 1% over 2 billion years
heterochrony
evolutionary change in timing of development
-characteristics can be added late in development and features are then moved to an earlier stage
paedomorphosis
terminal stages may be deleted causing adults of descendants to resemble youthful ancestors
- retention of ancestral juvenile characters by descendant adults
- ex. axolotl
allopatric speciation
allopatric pops. occupy separate geographical areas
- cannot interbreed because they are separated but could do so if geographical barriers were removed
- if these pops. evolve reproductive barriers, allopatric speciation occurs
- separate pops. evolve independently and adapt to different environments
- environmental change between pops. also can promote genetic divergences by favoring different phenotypes in the separated pops.
- eventually they become distinct enough they cannot interbreed when reunited (formation of new species)
- ex. sea urchin, galapagos finches
sympatric speciation
the evolution of 2 groups of the same species but they do not have a geographic barrier. These 2 groups evolve differently causing them to no longer be able to interbreed and are soon considered different species. Examples of this are the sculpins of Lake Baikel and various species of cichlid fishes in the great lakes of Africa which are found nowhere else.
gradualism
Darwin’s theory of gradualism opposes arguments for the sudden origin of species
- based on the accumulation of small changes over time which led to the different major forms of life
- “the accumulation of quantitative changes leads to qualitative change”
- agreed with Lyell’s uniformitarianism that past changes do not depend on catastrophic events not seen today
- natural pops. have small continuous changes in phenotypes that can accumulate over millions of years
punctuated equilibrium
proposed by Niles Eldridge and Stephen Jay Gould
- explains the discontinuous evolutionary changes observed through geological time (incomplete fossil records)
- states that phenotypic is concentrated in brief events of speciation followed by long intervals of morphological evolutionary stasis
- speciation is an episodic event
- duration of 10,000 - 100,000 years
- species survive 5-10 million years
- speciation may account for less than 1% of species life span
exaptation
denotes the utility of a structure for a biological role that was not part of the structures evolutionary origin
-exaptation contrasts adaption which implies that a structure arose by natural selection for a particular biological role
RNA world hypothesis
-first enzymes could have been RNA
-earliest self replicating molecules could have been RNA
-investigators call this stage the RNA world
the RNA world would have been encapsulated by membranous vesicular structures.
principles that guide zoological research
- theory of evolution
- chromosomal theory of inheritance
Darwin’s theory of evolution basics
- Darwin proposed this
- over 160 years old
- published in “on the origin of species by Means of Natural Selection” in England in 1859
- obstacle: it lacked a successful theory of heredity
- Ernst Mayr proposed that Darwin’s theory of evolution should be viewed as 5 major theories (perpetual change, common descent, multiplication of the species, gradualism and natural selection)
common descent
all forms of life descend from a common ancestor through a branching of lineages
- life’s history has the structure of a branching evolutionary tree known as phylogeny
- serves as the basis for our taxonomic classification of animals
multiplication of species
the evolutionary process produces new species by splitting and transforming older ones
natural selection
a creative process that generates novel forms from the small individual variations that occur among organisms within a population
evolution of autotrophic organisms
- in some areas nutrient supply began to dwindle as the number of heterotrophs increased
- at that point a cell capable of converting inorganic precursors to a required nutrient (autotrophs) would have selective advantage
- the evolution of autotrophic organisms required gaining enzymes to catalyze conversion of inorganic molecules to more complex ones
recapitulation theory
the biogenetic law by Ernst Haeckel proposed that ontogeny recapitulates phylogeny
- initial flawed notion based on Lamarck’s concept of the inheritance of acquired traits
- later revised by K.E. von baer who argued that early development were more widely shared among animal groups than later ones and can be affected by divergence
endosymbiotic theory
proposed that a pop. ancestral to eukaryotic cells, derived from and resembling anaerobic bacteria, evolved a nucleus and other intracellular membranes from infoldings of the cell membrane
founder effect
(a type of genetic drift) a bottleneck associated with the founding of a new geographic pop. is called a founder effect and may be associated with the formation of a new species
gene flow
the movement of genes from one population to another by migration of individuals between pops.
genetic drift
the chance fluctuation in allelic frequency from one generation to the next, including loss of alleles from the population
- the smaller the pop. the greater it will be affected by genetic drift
- if pop. size remains small for many generations in a row, genetic variation can be greatly depleted
- loss of variability is harmful to a species evolutionary success because it restricts potential genetic responses to environmental change
bottlenecks
(a type of genetic drift) large reduction in pop. size leading to increase significance of every evolutionary change
sexual selection
selection for traits that help obtain a mate but not necessarily for survival
- bright colors that can attract a mate/predators
- environmental changes and the role of predators can alter selective value of these traits
- makes fitness of the organism a complex problem affected by multitudes of forces
macroevolution
describes large scale events in organic evolution as seen in the fossil record
what links macroevolution and microevolution
speciation
isolecithal eggs
-very little yolk distributed evenly in cytoplasm
-cleavage is holoblastic
(found in echinoderms, mollusks, and mammals)
mesolecithal eggs
-moderate amount of yolk concentrated in the vegetal pole
-cleavage is holoblastic
(occurs in amphibians)
centrolecithal eggs
-much yolk concentrated in the center
-cleavage is meroblastic
(occurs in arthropods such as insects)
telolecithal eggs
-much yolk concentrated at vegetal pole
-cleavage is meroblastic
(found in birds, reptiles, most fish, and a few amphibians)
microevolution
the study of genetic change occurring within natural pops.
blind (incomplete) gut
- when the embryonic gut opens only into the blastopore
- some animals retain the blind gut and have to digest their food completely or must egest the undigested parts back up the mouth
- (found in invertebrates such as sea anemones)
complete gut
- most organisms have a complete pathway from the mouth to the anus
- the blastopore becomes the mouth in some creatures while becoming the anus in some
mesoderm
3rd germ layer
- lies between endoderm and ectoderm
- forms in 2 ways:
- proliferation of cells near the lip of the blastopore into the space between archenteron and the outer body wall
- pushing the central region of archenteron wall into the space between the archenteron and outer body wall
- diploblastic: 2 layers
- triploblastic: 3 layers
endoderm
inner layer of cells lining the gut
ectoderm
outer layer of cells surrounding the blastocoel
binomial nomenclature
- Linnaeus’s system of naming species
- 2 words normally in latin
- printed or italicized
- 1st word: the genus and is capitalized (noun)
- 2nd word: the specific epithet and is written in lower case (adjective)
typological species concept
- before darwin a species was considered a distinct and immutable entity derived from divinely created patterns
- a type specimen was labeled and deposited in a museum
- new specimens were always compared to this previously described representative specimen
- small differences from type one were considered accidental imperfections
- large difference leads to description of a new species
biological species concept
- proposed by theodosius dobzhansky and ernst mayr
- a species is a reproductive community of pops. (reproductively isolated from others) that occupies a specific niche in nature
- ability to successfully interbreed is central to the concept
- criteria of niche views members of a reproductive community to have common ecological properties
vertebrate hallmarks
all vertebrate embryos share chordate hallmarks
-dorsal neutral tube
-notochord
-pharyngeal gill pouches /w aortic arches
-ventral heart
-postanal tail
(all chordates look the same during embryonic stages indicating common ancestry
ecdysozoans
any member of a clade within protostomia whose members shed the cuticle as they grow; includes arthropods, nematodes, and several smaller phyla
clades
corresponds to a unit of evolutionary common descent that includes ancestral lineage of all descendants
evolutionary taxonomy
- retains basic structure of linnaean taxonomy
- evolutionary taxa must have a single evolutionary origin and must show unique adaptive features
- george gaylord simpson and ernst mayr
evolutionary and cladistic taxonomy
- accept monophyletic groups
- reject polyphyletic groups
- however they differ on accepting paraphyletic groups which has important evolutionary implications
derivatives of ectoderm
- nervous system and nerve growth
- the brain, spinal cord, outer epithelial structures develop from ectoderm
- ectoderm thickens to form a neural plate just above the notochord
- edges of neural plate fold to create elongated hollow neural tubes (anterior end enlarges and forms the brain and cranial nerves. posterior end forms the spinal cord and spinal motor nerves.)
- neural crest cells pinch off from neural tube and give rise to much of peripheral nervous system
- neural crest cells are unique to vertebrates and important to the evolution of the vertebrate head and jaws
derivatives of endoderm
- archenteron forms as the primative gut during gastrulation in frogs
- the endodermal cavity eventually produces (digestive tract lining, lining of pharynx and lungs, most of the liver and pancreas, thyroid, parathyroid glands and thymus)
- in other vertebrate the alimentary canal develops from the primative gut
- is folded off from the yolk sac by growth and folding of the body wall
derivatives of mesoderm
- most muscles arise from mesoderm along each side of neural tube
- divides into a linear series of somites (38 in humans) by splitting, fusion and migration
- these somites produce (axial skeleton, dermis of dorsal skin, muscles of the back, body wall and limbs)
5 species concepts
- phylogenetic species concept
- typological species concept
- biological species concept
- evolutionary species concept
- cohesion species concept
biological species concept problems
- lacks an explicit temporal dimension
- gives little guidance regarding the species status of ancestral pops. relative to their evolutionary descendants
- disagreement on the degree of reproductive isolation necessary for considering 2 pops. separate species
- boundaries between species may be difficult to locate
- interbreeding does not occur in asexual organisms which only do binary fission and budding
species concepts continued
- a sign of dynamic research and should not be considered discouraging
- cannot predict which species concept will remain useful in the future
- possible disagreements regarding species boundaries may identify interesting cases of evolution in action
- no single concept is comprehensive or final but all need to be understood so as to understand future concepts
monophyly
a monophyletic taxon includes the most recent common ancestor and all descendants of that ancestor
paraphyly
a taxon is paraphyletic if it includes the most recent common ancestor of all members of a group and some but not all descendants of that ancestor
polyphyly
- a taxon is polyphyletic if it doesn’t include the most recent common ancestor of all members of a group
- the group has a least 2 separate evolutionary origins
protostome
the blastopore becomes the mouth and the second unnamed opening becomes the anus
deuterstome
embryo develops through the blastula and gastrula stages and forms a complete gut. The blastopore becomes the anus and a second unnamed opening becomes the mouth as is indicated by root words in the name of this group
parthenogenesis
- the development of an embryo from an unfertilized egg or one in which the male and female nuclei fail to unite following fertilization
- sperm is not always required for development
- artificial parthenogenesis: eggs of some species can be artificially induced to initiate development w/o sperm
- natural parthenogenesis: some have eggs that develop normally in the absence of the sperm
organism development
a series of progressive changes in an individual from its beginning to maturity
- starts when a fertilized egg divides mitotically to produce multicelled embryo
- zygote
- blastula stage: blastocoel
- gastrula stage: gastrocoel, endoderm, ectoderm, blastopore
- complete gut forms
- acoelomate body, pseudocoelomate body, or coelomate body forms
why is extinction a necessary part of evolution
ex. the rise of mammals that were able to use the available resources due to dinosaur extinction leading to their adaptive radiation
- surviving lineages can evolve
- reduced competition for resources
