Background Flashcards
What does evolution refer to in biology?
the process by which living species have diversified since the origin of life on Earth
What are the 4 things to considered when exploring why something evolved?
Causes
Conditions
Constraints
Consequences
What are the different evolutionary processes/mechanisms? (4)
Say whether each is targeted or random
Natural selection and sexual selection (targeted)
Genetic Drift (random)
Non assortative mating (targeted)
Migration (neither targeted nor random)
What do phylogenetic reconstructions assume?
the degree of relatedness is reflected in the number of shared characters and the similarity in structure and that those shared characters represent homologies
What is a paraphyletic taxon
a single ancestral species but does not include all species
Define polyphyletic taxon
a grade derived from more than one ancestral species
What is a clade
all monophyletic taxa
What is a monophyletic taxon
a single ancestral species including all descendants
What is Galton’s problem
the problem of drawing inferences from cross-cultural data, due to the statistical phenomenon now called autocorrelation. (the different observations are not independent of one another)
Describe Linnaean classification (4)
- A system with 7 levels
- Each level is included in the level above it
- Levels get increasingly specific from kingdom to species
- Species have a binomial
nomenclature:
Homo sapiens
What are the 4 key definitions of species? Who proposed each?
Biological Species Concept, Mayr (1942, 1963, 1970)
Mate Recognition Species Concept, Paterson (1985)
Evolutionary Species Concept, Simpson (1951, 1961)
Ecological Species Concept
Describe the Biological Species Concept
Whose idea was it
Emphasis on what separates individuals of different species, with focus on barriers to gene flow, or reproductive isolation
Mayr, 1942
Describe The Mate Recognition Species Concept
Who described it first
Emphasis on what binds individuals of a species together, rather than what separates those between species, with focus on mate recognition systems
Paterson (1985)
Who first described The Evolutionary Species Concept?
What is it
Simpson (1951, 1961)
Emphasis on the evolutionary process of speciation, rather than the maintenance of species boundaries, defining species as evolving lineages.
What is The Ecological Species Concept
Van Valen (1976) modification of Simpson’s 1961 that places emphasis on the adaptive niche shared by evolving lineages
How do animals become reproductively isolated
PRE‐ZYGOTIC MECHANISMS
• Ecological (or habitat) isolation (organisms of different species don’t meet)
• Seasonal (or temporal) isolation (organisms of different species don’t meet)
• Ethological (or sexual) isolation (organisms of different species don’t have sex)
• Mechanical isolation (organisms of different species have sex, but there’s no transfer of gamets)
• Gametic isolation (organisms of different species have sex, there’s transfer of gamets, but gamets don’t fertilise)
POST‐ZYGOTIC MECHANISMS
• Hybrid inviability (egg fertilises, but does not develop)
• Hybrid sterility (egg fertilises, embryo develops, but hybrid does not reproduce)
• Hybrid breakdown (egg fertilises, embryo develops, hybrid is viable and reproduces, but the viability and/or fertility of its offspring is much reduced)
Give 3 advantages of the Biological Species Concept
offers an elegant mechanism for the maintenance of species boundaries
it is testable on extant taxa
it is not ambiguous in application
Give 6 drawbacks of the biological species concept
o more than one reproductive barrier between species may exist
o does not apply to asexually reproducing forms
o cannot be applied to fossils
o cannot be tested (in nature) among species that are geographically isolated
o cannot easily accommodate hybrids or hybrid zones, which are not uncommon in
nature (particularly in plants!)
o disconnect between degree of reproductive isolation and amount of morphological
or genetic divergence
How did Paterson (1985) describe this theory of species
what are 2 advantages of this concept
“(Species are) that inclusive population of individual biparental organisms which share a common fertilization system” (Paterson 1985)
it is testable on extant taxa
can be applied to fossils in relation to those parts of the mating/reproductive phenotype that fossilise or leave prehistoric traces
What are 2 drawbacks of the mate recognition species concept
o cannot be applied to asexual species
o cannot easily accommodate hybrids or hybrid zones. Unclear definition and delimitation of what
constitutes a sufficiently similar mating and reproductive phenotype to warrant inclusion in the same
species
Give a quotation from Simpson and Wiley describing the Evolutionary Species concept
“A lineage (an ancestral‐descendant sequence of populations) evolving separately from others and with its own unitary evolutionary role and tendencies” (Simpson 1961)
“…a single lineage of ancestral descendant populations of organisms which maintains its identity
from other such lineages and which has its own evolutionary tendencies and historical fate” (Wiley, 1978)
Why is the evolutionary species concept
a) useful (2)
b) not useful (3)
a) it approximates to what, in practice, taxonomists and palaeontologists use
Very useful because it accommodates the persistence of species distinctiveness in the presence of interbreeding (also that asexual organisms form species).
b) has a problem of circularity in the definition of what constitutes a
common evolutionary lineage
o has a problem in defining the limits of variation within a species
o does not offer insights into either the mechanisms by which a
species evolves or is maintained
What makes primates mammals? (6)
- Thermoregulation
- Nutritional efficiency
- Locomotion and posture
- Reproduction
- Complex life history
- Behavioural flexibility
What makes a mammal a primate? (7)
Distinct hands and feet
Distinct teeth and digestive system
Greater dependence on vision than smell
Distinct peripheral auditory system
Flexible locomotor skeletal system
Reproductive and developmental
traits
Social and behavioural traits
What is special about
a) primate hands and feet (4)
b) primate teeth and gut
a) • pentadactyl (mostly) • nails instead of claws (mostly) • grasping (mostly) • opposable hallux and pollex (mostly)
b)
• Conservative dental formula (mostly)
• Molars with relatively low cusps
• Large intestines with a fermentation chamber (caecum or appendix)
How does anatomy reflect a primate’s greater dependence on vision than smell
- Shortened rostrum (mostly)
* Forward facing eyes (binocular vision), surrounded by a bony ring or wall
What is special about a primate’s
a) reproductive/ developmental traits (5)
b) locomotion anatomy
a) • Long gestations • One or two infants per birth • Long periods of dependence on mother (mostly) • Relatively slow growth • Relatively large brains
b) • Unfused and highly mobile radius and ulna in the forelimb and tibia and fibula in the hindlimb • clavicle
What 6 things make humans great apes
• Large molars with low cusps • Suspensory body proportions • No tail • Long gestation, 1 infant/birth, long reliance on mother/group, very slow growth, larger brains • Male kin‐bonding? • Use of technology
What 6 things make humans unique
• Small canines • Bipedal locomotion (and correlated adaptations) • Manufacture of technology • Extra large brains • Childhood phase in life‐history • Complex language
What are the different definitions of ‘adaptation’
Adaptation (Darwinian sense): traits that promote survival (=viability) and successful reproduction
Adaptation (Neo‐Darwinian & Fisherian sense): traits that promote reproductive success (fitness)
What is the Fisherian sense of adaptation
outcome of natural selection
What are the conditions and constraint generally when considering adaptations to diet
Conditions: what other animals are eating, how seasonal the fruiting trees are etc
Constraints: body size, can babies digest it etc
