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

missing links

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

speciose

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

3

biological systematics

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

4

alpha taxonomy

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

holotype

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

sister taxon

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

basal

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

8

megadont

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

9

synchronic

at the same time; thus synchronic species coexist in time

10

Neogene period

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

aridification

a drying trend resulting from lower seasonal or annual precipitation levels

12

mosaic habitats

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

13

savannah hypothesis

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

14

gallery forest

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

15

forest hypothesis

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

variability selection hypothesis

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

aligned sequence

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

recurrent mutation

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

genetic divergence

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

20

species divergence

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

alveoli

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

22

assemblages

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

23

foramen magnum

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

24

stem hominin

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

25

proximal

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

distal

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

27

phalanx

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

28

muscle markings

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

craniodental

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

30

eurytopic

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"