EVOLUTION Flashcards

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1
Q

EVIDENCE FOR EVOLUTION

A
  1. fossil record:
    -the identification, interpretation and dating of fossils gives us some of the most direct evidence for evolution
  2. biogeography:
    -the study of where species occur, and why. this is based on the finding that different regions with similar climatic conditions contain very different animals and plants
  3. modification by descent:
    -similar structures with same body plan that perform different functions are known as homologous structures
    -homologous structures provide evidence of evolution because the similarities suggest a common ancestor
  4. genetic evidence:
    -closely related organisms have more similarities in their DNA
    -shows how changes in genotype and phenotype are transferred to successive generations
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2
Q

DIFFERENCE BETWEEN HYPOTHESIS AND A THEORY

A

hypothesis:
* a tentative explanation of a phenomenon that can be tested and may be accepted or rejected

theory:
* explanation of an observation that is supported by facts, models and laws

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3
Q

CONTRIBUTION OF VARIOUS SOURCES OF VARIATION

CRRRM

A

MEIOSIS:
* crossing over involving the exchange of genetic material during prophase 1 leads to the formation of gametes with different gene combinations
* the random assortment of homologous chromosome pairs on the equator during metaphase 1 also leads to greater variation

REPRODUCTION:
* random fertilisation where different gene combinations are formed which increases variation in species
* random mating of individuals and successful fertilisation occur in a population, the variety of gene combinations formed is even greater

MUTATIONS:
* changes in sequence of nucleotides may lead to change in the amino acid sequence of protein synthesised

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4
Q

CONTINUOUS VARIATION

A
  • a type of variation that has a range of phenotypes for the same characteristic
  • no distinct categories, no limit on value, tends to be quantitative
  • height, weight, heart rate, etc.
  • represented by line graph, histogram
  • controlled by a lot of genes and the environment
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5
Q

DISCONTINUOUS VARIATION

A
  • a type of variation where phenotypes fit into seperate categories with no intermediate forms
  • distinct categories, tends to be qualitative
  • tongue rolling, fingerprints, eye colour
  • represented in a bar graph
  • controlled by a few genes
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6
Q

IDEAS ON EVOLUTION IN ORDER OF ORIGIN

A
  1. lamarckism
  2. darwinism
  3. punctuated equilibrium
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7
Q

THEORY OF LAMARCK

A

LAW OF THE INHERITANCE OF ACQUIRED CHARACTERISTICS:
* characteristics developed during the life of an individual can be passed on to their offspring

LAW OF USE AND DISUSE:
* as an organism uses a structure or organ more regularly, it becomes better developed or enlarged. if an organism does not use a structure or organ frequently, it becomes less developed or reduced in size and may disapear altogether

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8
Q

REASONS FOR LAMARCK’S THEORY BEING REJECTED

A
  • there is no evidence that acquired characteristics are inherited to the DNA of an organism’s gametes
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9
Q

DARWIN’S THEORY OF EVOLUTION OBY NATURAL SELECTION

A
  • organisms produce a large number of offspring
  • there is a great deal of variation
  • some have favourable characteristics and some do not
  • when there is a change in the environmental conditions or if there is a competition,
  • then organisms with characteristics, which make them more suited, survive
  • whilst organisms with unfavourable characteristics, which make them less suited, die
  • the organisms that survive, reproduce
  • and thus pass on the allele for the favourable characteristic to their offspring
  • the next generation will therefore have a higher proportion of individuals with the favourable characteristic
  • in this way, the characteristics of a population gradually change over a long period of time
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10
Q

PUNCTUATED EQUILIBRIUM

A
  • evolution involves long periods of time where species do not change or change gradually through natural selection.
  • this alternates with short periods of time where rapid changes occur through natural selection
  • during which new species may form in a short period of time
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11
Q

DEFINITION OF BIOLOGICAL EVOLUTION

A
  • a change in the gene pool of a population over millions of years
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12
Q

DEFINITION:
1. POPULATION
2. SPECIES

A
  1. a group of organisms of the same species that occupy the same area at a same time
  2. a group of organisms with similar characteristics that can interbreed to produce fertile offspring
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13
Q

PROCESS OF SPECIATION

A
  • if a population of a single species
  • becomes seperated by a geographical barrier
  • then the population splits into two
  • there is now no gene flow between the two populations
  • since each population may be exposed to defferent environmental conditions
  • natural selection occurs independently in each of the two populations
  • such that the individuals of the two populations become very different from each other
  • genotypically and phenotypically
  • even if the two populations were to mix again they will not be able to interbreed
  • and therefore a new species has formed
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14
Q

SPECIATION THROUGH GEOGRAPHICAL ISOLATION IN THE FOLLOWING

A
  1. galapagos finches
  2. galapagos tortoises
  3. plants on different land masses
    -baobabs in africa and madagascar
    -proteas in south africa and austrailia
  4. any example of mammals on different land masses
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15
Q

EXAMPLES OF REPRODUCTIVE ISOLATION THAT KEEPS SPECIES SEPERATE

A
  1. breeding at different times of the year
  2. species-specific courtship behaviour
  3. adaptation to different pollinators in plants
  4. infertile offspring
  5. prevention of fertilisation
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16
Q

EXAMPLES OF NATURAL SELECTION AND EVOLUTION IN PRESENT TIME

A
  1. use of insecticides and consequent resistance to insecticides in insects
  2. development of resistant strains of TB causing bacteria to antibiotics, due to mutations in bacteria and failure to complete antibiotic courses
  3. HIV resistance to antiretroviral medication
  4. bill and body size of galapagos finches
17
Q

HOW BACTERIA DEVELOPS RESISTANCE TO ANTIBIOTICS

A
  • bacteria populations develop resistance by natural selection
  • bacteria reproduce rapidly
  • within the population, mutations occur which may produce bacteria that are resistant to antibiotics
  • mutations introduce variation within the population making some bacteria resistant to antibiotics while others are not
  • antibiotics kill non-resistant and the resistant bacteria survive
  • the resistant bacteria reproduce and pass on their mutated genes to their offspring producing a bacterial population with a greater proportion of resistant bacteria
18
Q

PHYLOGENETIC TREE OF THE FAMILY HOMINIDAE IN THE ANIMAL KINGDOM

A
19
Q

PHYLOGENETIC TREE OF THE FAMILY HOMINIDAE IN THE ANIMAL KINGDOM

A

file:///C:/Users/sagem/Dropbox/PC/Downloads/Photo%20(4).pdf

20
Q

CHARACTERISTICS THAT HUMANS SHARE WITH AFRICAN APES

A
  • two hands, each with five fingers; two feet each with five toes
  • long arms that rotate freely as shoulder joints allow movement in all directions
  • naked fingertips and toes ending in flat nails
  • reduced snout with weakened sense of smell
  • stereoscopic vision as the eyes face forward providing depth of field
  • eyes have cones and rods making colour vision possible
  • brain centres that process information from hands and eyes are enlarged
  • no tail
  • sexual dimorphism where males and females are clearly distinguished
  • have molars and premolars with rounded cusps
21
Q

ANATOMICAL DIFFERENCES BETWEEN AFRICAN APES AND HUMANS

A

BIPEDALISM:
* humans - foramen magnum in a forward position. more curved spine. short-wide pelvis
* african apes - foramen magnum in a backward position. less curved spine. long, narrow pelvis

BRAIN SIZE:
* humans - large frontal area, which requires a large cranium and a higher forehead to house and protect it.
* african apes - smaller brain, less developed

TEETH (DENTITION):
* humans - small teeth. canine is smaller. no gaps between incissors and canines.
* african apes - large teeth. large canines. gaps between incisors and canines

PROGNATHISM:
* humans - shorter jaw. does not need strong muscles for their diet of softer foods. face is small and flatter in the front.
* african apes - longer jaw. stonger muscles required for their diet of tough foods. face is large and protruding in the front.

PALATE SHAPE:
* humans - palate is small and semi-circular in shape
* african apes - palate is long and rectangular in shape

CRANIAL RIDGES:
* humans - no cranial ridge as humans have smaller jaws and do not need large jaw muscles
* african apes - cranial ridge across the top of the cranium

BROW RIDGES:
* humans - not well developed. more upright brow, which holds a larger brain
* african apes - brow ridges well developed

22
Q

FOSSIL EVIDENCE

A
  • evidence from fossils of different ages show that the anatomical characteristics of organisms changed gradually over time.
23
Q

FOSSIL : ARDIPITHECUS

A
  • age: 5 - 4 mya
  • scientist : tim white
  • found in the afar valley of ethiopia

anatomical features:
* brain size: 300-350 ml
* forward position of foramen magnum
* protruding jaws
* heavy brow ridges
* pelvis structure: bipedal and tree climbing

24
Q

FOSSIL : AUSTRALOPITHECUS AFARENSIS (LUCY)

A
  • age: 4 - 2.7 mya
  • scientist: donald johnson
  • found in the afar valley in ethiopia

anatomical features:
* brain size: 375-550 ml
* forward position of foramen magnum
* bipedal
* protruding jaws
* heavy brow ridges
* canines large and pointed

25
Q

FOSSIL : AUSTRALOPITHECUS AFRICANUS (TAUNG CHILD)

A
  • age: 3 - 2 mya
  • scientist: raymond dart
  • found in the cradle of humankind: taung; sterkfontein

anatomical features:
* brain size: 428-625 ml
* forward position of foramen magnum
* protruding jaws
* brow ridges
* bipedal
* used stone tools
* teeth large, canines not long

26
Q

FOSSIL : AUSTRALOPITHECUS SEDIBA (KARABO)

A
  • age: 1.9 - 1.78 mya
  • scientist: lee berger
  • found in the cradle of humankind: malapa area

anatomical features:
* gracile
* rigid feet
* long arms
* brain case size: 420m cubed
* face is less prognathous

27
Q

FOSSIL : HOMO HABILIS

A
  • age: 2.2 - 1.6 mya
  • scientist: louis abd nary leakey
  • found in tanzania

autonomical features:
* brain size: 650 ml
* less prognathous
* bipedal
* used stone tools
* human-like teeth, smaller canines

28
Q

FOSSIL : HOMO ERECTUS

A
  • age: 2 - 0.4 mya
  • scientist: eugene dubois
  • found in kenya

anatomical features:
* brain size: 900 ml
* protruding jaw
* cranial ridge
* used stone tools and fire
* short canines

29
Q

FOSSIL : HOMO SAPIENS

A
  • age: 200 000 years ago - present
  • scientist: tim white
  • found in the cradle of humankind: makapansgatin, limpopo; border cave in KZN; blombos cave

anatomical features:
* brain size: 1200 - 1800 ml. the increased cranium size allows a larger brain to develop
* bipedal
-the foramen magnum is located in a more forward position
-the pelvis is wider and shorter
-the spine is S-shaped
* no brow ridges
* smaller canines can chew food that was cooked or made soft using fire.

30
Q

THE OUT OF AFRICA HYPOTHESIS

A
  • the ‘out of africa’ hypothesis states that modern humans originated in africa and then migrated out of africa to other continents.
31
Q

EVIDENCE TO PROVE THE OUT OF AFRICA HYPOTHESIS

A

FOSSIL EVIDENCE:
* the fossils of ardipithecus have only been found in africa
* the fossils of australopithecines have only been founf in africa
* the fossils of homo habilis have only been found in africa
* the oldest fossils of homo erectus have been found in africa
* the oldest fossils of homo sapiens have been found in africa

GENETIC EVIDENCE:
* mitochondrial DNA is inherited only from the maternal line.
* analysis of mutations on this mitochondrial DNA shows that the oldest female ancestors were located in africa and that all humans descended from her