Chapter 9: Hominin Origins: From Ape to Australopithecine Flashcards Preview

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Flashcards in Chapter 9: Hominin Origins: From Ape to Australopithecine Deck (43)
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1
Q

missing links

A

a popular term referring to transitional fossils, which typically bear a combination of primitive and derived traits linking them with earlier and later forms within a clade

2
Q

speciose

A

literally, “full of species,” indicating a taxonomy consisting of many rather than fewer named species

3
Q

biological systematics

A

the formal science of classification and taxonomy, specifying a set of rules and guidelines for categorizing biological diversity and deriving phylogenies

4
Q

alpha taxonomy

A

the process of classifying organisms to genus and species, based on extensive data extracted from morphology, behaviour, DNA and so on. In the case of fossil species, detailed analyses of skeletal and dental morphology are essential elements in deriving the alpha taxonomy.

5
Q

holotype

A

the specimen that serves as the “name-bearer” of a fossil species and from which a description of the salient features of the taxon are obtained. It need not be the sole source of information for identifying a member of the taxon, nor does the holotype need to be a typical example

6
Q

sister taxon

A

in systematics, sister taxa are those forms that are related by virtue of a divergence event and that share a last common ancestor; panins and hominins are sister taxa, as are Australopithecus an Ardipithecus

7
Q

basal

A

a qualitative term distinguishing the earliest widely accepted hominins from those forms later assigned the genus Homo

8
Q

megadont

A

literally, large teeth; megadont hominins are characterized by expansion of the posterior teeth (i.e., premolars and molars)

9
Q

synchronic

A

at the same time; thus synchronic species coexist in time

10
Q

Neogene period

A

a geological time period comprising the Miocene and Pliocene epochs, associated with global climate change and diversification of a number of avian and mammal species, particularly open woodland and grassland forms

11
Q

aridification

A

a drying trend resulting from lower seasonal or annual precipitation levels

12
Q

mosaic habitats

A

areas characterized by a range of habitat types, from forest to grassland

13
Q

savannah hypothesis

A

the now discredited idea that the development of open savannah grassland created conditions leading to the evolution of hominins

14
Q

gallery forest

A

dense, canopied forest found along water courses such as rivers and lakeshores

15
Q

forest hypothesis

A

the suggestion that the hominin clade diverged from panins while still occupying a woodland/forest habitat, as suggested by paleoecological reconstruction of forest localities

16
Q

variability selection hypothesis

A

a model that suggests that the operating factor in hominin evolution was environmental disparity, rather than stability, which promoted adaptive flexibility in hominin traits, including locomotion, dental adaptations, and technology

17
Q

aligned sequence

A

in molecular genetics research, sequences of DNA (or RNA) derived from homologous sites within the genome are literally arranged or aligned to identify similarities and differences between two species, the latter resulting from, for example, point mutations, insertions, or deletions

18
Q

recurrent mutation

A

a mutation that tends to occur repeatedly at the same locus; a number of genetic disorders are maintained at high frequencies through recurrent mutation (e.g., Marfan syndrome in humans, leading to impaired collagen formation)

19
Q

genetic divergence

A

an estimate of the time since two genomes diverged, based on the number of differences observed and assuming a constant rate of mutation

20
Q

species divergence

A

an estimate of time since speciation; because genetic differences are constantly accumulating with in lineages, estimates of genetic divergence time will always be older than species divergence time

21
Q

alveoli

A

the bony sockets for teeth present in the upper and lower jaws

22
Q

assemblages

A

the collection of all remains of plants or animals from paleontological contexts

23
Q

foramen magnum

A

“large passage,” the foramen magnum is the largest hole in the cranium, through which the brain stem passes to become the spinal cord

24
Q

stem hominin

A

the progenitor of all later hominin species within a clade, arising from the last common ancestor

25
Q

proximal

A

in skeletal anatomy, a position closer to the midline of the body (e.g., the elbow is distal to the shoulder joint); in teeth, the term refers to the tooth surface facing the back of the mouth

26
Q

distal

A

in anatomy, a position farther from the midline of the body

27
Q

phalanx

A

one of a series of short bones that make up the fingers in the hand or the toes in the foot

28
Q

muscle markings

A

impressions on a bone surface that define the point of origin or insertion of a muscle; activities that build up muscles can also create more prominent muscle markings

29
Q

craniodental

A

a descriptive term referring to the hard tissues, bone, and teeth comprising the skull

30
Q

eurytopic

A

organisms that are able to live in diverse habitats and geographic ranges; the prefix “eury” means “broad, wide” and the affix “topic” refers to “place”

31
Q

gracile

A

small or slightly build; among australopithecines, refers to those species lacking the skeletal and dental features associated with the megadont adaptation

32
Q

robust

A

rugged or strongly built; several australopithecine species possess skeletal and dental features associated with large chewing muscles and crushing and grinding of hard foods

33
Q

percussive stone tools

A

implements fashioned by purposefully striking one stone against another to produce a cutting edge

34
Q

phyletic sequence

A

an unbroken lineage of ancestor-descendant species

35
Q

punctuated anagenesis

A

speciation has two tempos, slow and gradual (anagensis) or rapid followed by stasis (punctuated equilibrium); punctuated anagenesis combines these into a pattern of rapid change within a continually evolving lineage; the possibility of punctuated anagenesis is not universally held among evolutionary biologists

36
Q

mandibular symphsis

A

the midline of the lower jaw, where the left and right sides of the dental arcade meet

37
Q

orthognathic

A

“ortho” refers to vertical or flat, and “gnathic” to the jaws; thus, “orthognathic” means “flat face”

38
Q

breccia

A

a rock formation composed of stone fragments embedded within a fine-grained cement-like matrix

39
Q

prognathic

A

refers to the degree to which the lower face projects forward

40
Q

competitive exclusion

A

a phenomenon in which two species closely related in phenotype and ecology come into direct competition for resources. In these cases one species will either become extinct or adopt a new phenotype (morphology and/or behaviour), allowing it to exploit other resources.

41
Q

Liem’s Paradox

A

a model in biology that describes the apparent paradox between a specialized phenotype and a generalized behaviour; the paradox is resolved if the specialized phenotype does not restrict an organism from nonspecialized behaviours

42
Q

fallback foods

A

resources on which a species relies when its preferred, more easily acquired and processed foods are unavailable

43
Q

homoiology

A

similarities that occur among organisms by virtue of a bone’s ability to respond to existing mechanical forces; similar behaviours will reproduce such forces and thus the associated morphology, which may be confused with genetic relationships