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Human Biology: Unit 4 > Chapter 11 - Other Evidence of Evolution > Flashcards

Chapter 11 - Other Evidence of Evolution Flashcards

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1
Q

What is FOSSIL?

Examples

A

Any well-preserved trace or part of an organism that lived a long time ago.
- A fossil is any preserved remains, impression, or trace of any once-living thing from a past geological age.

eg. PARTS OF AN ORGANISM
- Bones, shells, teeth
OTHER
- footprints, burrows, faeces, or impressions of all or part of an animal or plant.

Human ancestors = bones, teeth, sometimes footprints

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2
Q

What is an example of a human ancestor and its fossil remains

A

The ancestor of Modern Human = Australopithecus afarensis

- Fossil remains found in the Hadar, region of Ethiopia

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3
Q

Why are fossils and remains of organisms’ important?

A

Extremely important as they allow scientists to
- DETERMINE exactly what EXTINCT Species were like.

Other material associated with bones such as the rock which they were found and fossils of other plants and animals, allow the scientists to
- DEVELOP A PICTURE OF LIFE IN THE PAST - what the organism ATE, what OTHER organism EXISTED at the TIME, CLIMATE CONDITIONS.

FOSSIL RECORD has allowed scientists to BUILD A SEQUENCE of the EVOLUTION of a PARTICULAR PLANT/ANIMAL.
eg. Horse (best example) - traced from fossil remains to have been evolved from creature not much bigger than a small dog to current horse.

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4
Q

What happens if conditions for fossilisation does not come into effect?

What are the 2 main CONDITIONS FOR FOSSILISATION IN TERMS OF DECAY?

A

Billions of organisms have lived on Earth, the Chance that a plant or animal will be fossilised is very small.
- BECAUSE normally, dead organisms are DECAYED by MICRO-ORGANISMS and NO TRACE OF EXISTENCE is left.

CONDITIONS FOR FOSSILISATION
1. Parts/organism may be fossilised when BURIED BY DRIFTING SAND, MUD DEPOSITED BY RIVES, VOLCANIC ASH, OR (HUMAN ANCESTORS) MEMBERS OF A SPECIES.

  1. if BURIED RAPIDLY, CONDITIONS MAY NOT BE SUITABLE FOR THE ACTIVITY OF DECAY ORGANISMS (DECOMPOSERS), AND THE DECOMPOSITION WILL BE SLOW OR PREVENTED.
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5
Q

What is the effect of soil type on fossilisation? (FOR BONE)

WHAT ARE THE GOOD CONDITIONS?
- EXPLANATION

WHAT ARE THE BAD CONDITIONS
- EXPLANATION

A

NATURE OF SOIL = is very important for the FOSSILISATION OF BONE (OR OTHER FORMS OF TISSUE)

BAD CONDITIONS OF SOIL
- WET,
- ACIDIC SOIL
Causes the bone to be DISSOLVED, = no fossilisation occurs.
- Oxygen present = decomposers will be abundant and able to survive - cause decay to organism body.

GOOD CONDITIONS OF SOIL
1. No OXYGEN; as in the case of peat, complete preservation of soft tissues and the bones of the animal may occur.

  1. ALKALINE soil = BEST FOSSILS PRODUCED
    Because the MINERALS IN THE BONE ARE NOT DISSOLVED.
    - NEW MINERALS (eg. Lime or iron oxide) are DEPOSITED in the PORES of the BONE, REPLACING THE ORGANIC MATTER THAT MAKES UP ABOUT 35% by weight of the bone.
    - Bone becomes PETRIFIED (TURNED INTO ROCK), but the DETAILS OF THE STRUCTURE ARE STILL PRESERVED.
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6
Q

Where are Fossils usually located and explain how and why they are preserved in each location.

A

Examples of Location in which human or other organism fossils are found =

  • EDGES OF ANCIENT LAKES AND RIVER SYSTEMS,
  • IN CAVES OR VOLCANICALLY ACTIVE AREAS

this is because the organisms can be BURIED RAPIDLY, PREVENTING DECOMPOSITION.

  1. RIVERS AND LAKES BUILD UP SEDIMENTS WHEN FLOODING OCCURS OR WHEN THE WATER FLOW SLOWS RAPIDLY.
  2. many CAVES are in Limestone (CALCIUM CARBONATE)
    This chemical may be deposited around DEAD organisms,
    - or the cave roof or walls may COLLAPSE, covering the bodies of animals.
  3. unusual for animals to be preserved NEAR VOLCANIC ERUPTIONS - because the HEAT FROM THE VOLCANIC MATERIAL DESTROYS THE ORGANISMS
    - but in EAST AFRICA ASH FALLS HAVE PRESERVED FOSSILS OF MANY HUMAN ANCESTORS.
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7
Q

How are fossils usually found?

A
  1. Fossils sometimes found by CHANCE
    - at the SURFACE OF THE GROUND where they might have been UNCOVERED DUE to EROSION.

OFTEN DISCOVERY OF FOSSILS IS THE RESULT OF SLOW AND PAINSTAKING

  1. EXCAVATION OF LIKELY SITES.
    - surface discoveries such as fossil fragments, or evidence of human occupation such as that found in many CAVES, are INDICATIONS, of the places where excavations may PROVE FRUITFUL.
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8
Q

What is Excavation?

What are the steps

A

Excavation = ‘the dig’

  • In archaeology, excavation is the exposure, processing and recording of archaeological remains.
  • These locations range from one to several areas at a time during a project and can be conducted over a few weeks to several years.
  1. SURFACE DISCOVERIES such as fossil fragments, or evidence of human occupation such as that found in many CAVES, are INDICATIONS, of the places where excavations may PROVE FRUITFUL.
  2. the area to be Investigated is SURVEYED AND MARKED OUT IN SECTIONS
  3. SMALL HAND TOOLS are used to REMOVE SOIL GENTLY so as NOT TO DAMAGE ANY OF THE MATERIAL.
  4. THE SOIL REMOVED is usually SIEVED so that even very SMALL FRAGMENTS are NOT OVERLOOKED
  5. PHOTOGRAPHS are Taken at every stage of a dig so that DETAILED STUDIES of the POSITIONS of UNCOVERED MATERIAL can be CARRIED out LATER.
  6. EACH ITEM IS carefully LABELLED AND CATALOGUED for the PROLONGED STUDY THAT FOLLOWS THE EXCAVATION OF THE SITE.
  7. IN THE LAB. Fossil bones AND ARTEFACTS are carefully SCRAPED CLEAN, BROKEN PARTS ARE POEICED TOGETHER, MEASUREMENTS ARE TAKEN.
  8. PLASTER CASTS OR LATEX MOULDS MAY BE MADE
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9
Q

What are artefacts?
examples?

In which case are artefacts found?

A

Artefacts = objects that have been deliberately made by humans

examples = stone tools, beads, carvings, charcoal from cooking fires and cave paintings.

Found in the case of fossils of human ancestors - artefacts are found in association with the fossils.

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10
Q

What is dating?

Why is it important?

A

One of the major tasks following the excavation of fossils or artefacts

DETERMINING THE AGE OF THE FOSIISL/MATERIAL

knowledge of the age is crucial in FINDING OUT THE SEQUENCE OF CHANGES THAT HAVE RESULTED IN PRESENT-DAY HUMANS or species.

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11
Q

What are the two different types of dating?

Explain them.

A

Various methods of dating exist - which can provide

  1. ABSOLUTE DATES - the actual age of the specimens
    - methods are LIMITED in their application because each depends on the occurrence of a particular set of circumstances before it can be sued
    - do give a number of ways of determining the actual age of ancient material
    - new methods are being developed, with constant improvements of accuracy older methods
  2. RELATIVE DATES - A Comparison of fossils to tell us whether one sample is Older or Younger than other
    - determining the relative order of past events, without necessarily determining their absolute age.
    - considered in relation or in proportion to something else.
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12
Q

What has modern tech. allowed fossils to be dated?

A

Modern Tech has ENABLED ACCURATE ESTIMATES to be MADE of the ABSOLUTE AGE of many samples.

However, when that is not possible, knowing whether one fossil is older or younger than another is very important.

The age (or date) of a fossil or artefact is usually given in years before the present time.
eg. A fossil may be said to date from 45 000 yrs BP, which is another way of saying it is 45 000 yrs.

BP = before present

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13
Q

Examples of Absolute dating.

Examples of Relative dating

A

Absolute dating

  • Potassium-argon dating
  • Carbon-14 dating

Relative dating

  • Stratigraphy
  • Tree-ring dating
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14
Q

What is potassium-argon dating?

A

Absolute dating technique that is based on the decay of radioactive potassium top form Calcium and Argon.

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15
Q

What are Isotopes?

A

Isotopes are atoms of the same element with different numbers of neutrons.

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16
Q

What are the isotopes of Potassium?

What is used in K-Ar dating?
why is it used?

A

K all have 19 protons
K-39 =. 20 N
K-40 = 21 N
K-41 = 22 N

K-40

  • radioactive isotope and DECAYS TO FORM Ca-40 or. Ar-40.
  • such decay takes place at an extremely SLOW BUT CONSTANT RATE,
  • so determining the amounts of K-40, Ar-40 in a rock sample enables the age of the rock to be calculated.

As the rock AGES, the PROPORTION OF K-40 DECREASES WHILE THE Ar-40 INCREASES.

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17
Q

What are the limitations of K-Ar dating?

A
  1. Not all rock types are suitable for this method of dating
  2. Can only DATE ROCKS OLDER THAN 100 000 - 200 000 years.
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18
Q

Define Half-life

A

The time required for half of any quantity of radioactive material to decay into stable non-radioactive material

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19
Q

Explain the half-life of K.

Why can it only date samples older than 200 000 yrs

A

The half-life of K-40 is 1250 BILLION YEARS (1.25 x 10^9)
- this means it takes 1250 billion years for half of the K-40 to decay.

  • therefore after 100 000 YRS ONLY 0.0053% OF THE K-40 in a rock would have decayed to argon-40.

Such a small amount pushes the limits of detection services currently in use.
- hence it is more useful on samples that are older than 200 000yrs.

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20
Q

How to use K-Ar dating to determine the age of a sample?

A
  1. Some suitable rock of the same age as the fossil must be available
  2. The age of the rock is determined Using K-Ar dating, and hence the age of the fossil is INFERRED.
  3. the situation can occur when rocks PRODUCED IN VOLCANIC ERUPTIONS BURY BONES
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21
Q

What is Carbon-14 dating?

A

The radiocarbon dating method is based on the DECAY of the RADIOACTIVE ISOTOPE OF CARBON (C), to Nitrogen.

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22
Q

How is Carbon-14 produced?

A
  1. Carbon-14 is produced in the UPPER ATMOSPHERE by the action of the cosmic radiation (emitted from stars), ON NITROGEN (N) at about the SAME RATE AT WHICH IT DECAYS
  2. In the atmosphere there is a RATIO OF ONE C-14 TO VERY MILLION MILLION (10^12) ATOMS OF THE STABLE ISOTOPE CARBON-12.
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23
Q

How does radioactive C-14 enter tissue of organisms?

A

When green plants use atmospheric Carbon dioxide in photosynthesis, 1 atom in every million of the C atoms incorporated in the plant tissues is C-14.

Should an animal eat the plant, the C-14 then becomes part of the animal’s tissues.

With death, an organism’s intake of C-14 ceases, but the C-14 already in the tissues of the organism COINTUNUES TO DECAY AT A FIXED RATE.

24
Q

How can the Isotope C-14 dating technique be used to identify the age of the sample?

Explain the half-life of C-14 and its ratio.

A

Measuring the amount of RADIATION LIBERATED BY A SAMPLE, THE RATIO of the C-14 to the C-12 can be estimated., AND FROM THIS AGE OF THE SAMPLE CAN BE CALCULATED.

The ratio of radioactive carbon in the issues of living organisms today is
- 1 C-14 to very 10^12 C-12 atoms

The ratio DECLINES to 0.5 IN 10^12 AFTER 5730 YEARS then to 0.25, after another 5730 years
so on..

HALF-LIFE OF C-14 = 5370 YEARS

25
Q

What is ACCELERATOR MASS SPECTROMETRY RADIOCARBON DATING?

What are the 2 main steps?

How C-14 does other C-14 dating techniques need?

A

AMS radiocarbon dating = a more refined technique

  1. A sample of 100 micrograms (0.0001 grams)
  2. Involves BREAKING THE SAMPLE UP INTO ITS CONSTITUENT atoms so that the number of atoms of each ISOTOPE of CARBON can be COUNTED.

OTHER C-14 DATING PROCEDURE NEEDS
- Requires at least 3 grams of organic material so that the RATE of radioactive CARBON-14 can be measured.

26
Q

Explain an example when C-14 dating proved useful.

A

AMS made it possible to date CAVE PAINTINGS ACCURATELY FROM TINY SAMPLES OF PIGMENT.

  • Such pigment often contain organic material such as Charcoal, while honey, milk, blood or soil seed TO BIND THE PIGMENT PARTICLES
27
Q

Limitations of C-14 dating

Benefits?

A

LIMITATIONS
1. After 70 000 yrs the % of C-14 left is only 0.021%
This is TOO SMALL to be able to MEASURE ACCURATELY, Therefore the C-14 dating method back NOT MORE THAN 60 000 Yrs.

  1. Material to be dated must CONTAIN ORGANIC MATERIAL (compounds from living things that contain Carbon).
  2. It was once assumed that the ratio of C-14 to C-12 was constant in the atmosphere, but now it is known that the amount of C-14 IN THE ATMOSPHERE VARIES
    - hence deduced age must be Treated with a DEGREE OF CAUTION.

BENEFITS
1. dates fossils and artefacts of recent origin because these are often found in association with Charcoal left from cooking fires.

By dating charcoal found in ancient hearths, the approx age of artefacts can be deduced

  1. CORRECTIONS FOR THE FLUCTIONSATION OF C-14 content in the atmosphere is now possible for the past 9000 yrs, BY REFERENCE OF OTHER INFORMATION such as tree-ring dating.
28
Q

What is Stratigraphy?

What are the 2 useful ways it dates fosiils?

A

The study of layers or strata.

USEFUL IN 2 WAYS in dating fossil material

  1. Principle of SUPERPOSITION
    - assumes that in the layers of the SEDIMENTARY ROCK the layers at the TOP ARE THE YOUNGEST, THAN THOSE BENEATH THEM.
  2. CORRELATION OF ROCK STRATA
    - involves matching the LAYERS of ROCK from different areas

this makes relative dating of strata more precise

29
Q

Explain the principle of SUPERPOSITION

Negatives?

A

Principle of SUPERPOSITION

  • assumes that in the layers of the SEDIMENTARY ROCK the layers at the TOP ARE THE YOUNGEST, THAN THOSE BENEATH THEM.
  • thus any fossils/material found in the top layers will be younger than the material found below them
  • THIS PRINCIPLE NEEDS TO BE APPLIED WITH CARE BECAUSE OF LIMITATIONS
    1. DISTORTIONS IN THE EARTH’S CRUST DO OCCUR
  1. SEQUENCES OF ROCK MAY BE TURNED UPSIDE DOWN
  2. POSSIBLE FOR ARTEFACTS/FOSSILS TO BE BURIED BY ANIMALS, EARLY HUMANS, SOMETIME AFTER THE DEPOSITIONS OF THE SEDIMENT.
    - in this case, the specimen may be younger than the layers above it
30
Q

EXPLAIN CORRELATION OF RCOK TRATA AND INDEX FPOSSILS

A

CORRELATION OF ROCK STRATA
- involves matching the LAYERS of ROCK from different areas

  1. Can be done by examining the ROCK ITSELF
  2. STUDYING the fossil it contains
    - Rocks that contain the same fossils may be assumed to be the same age

Certain Fossils called INDEX FOSSILS - are of great value in this correlation work BECAUSE THEY ARE WIDELY DISTRIBUTED AND WERE PRESENT ON EARTH FOR ONLY A LIMITED PEOID OF TIME.

this makes relative dating of strata more precise

31
Q

What is dendrochronology?

A

Tree growth ring dating
the material used = wood
thicker - more resources available
Useful rang in years BP - up to 9000

32
Q

Explain the analysis of fossilised grains?
how they occur?
why are they useful?

A

Analysis of fossilised grains have developed into an important branch of science

  • fossil pollen grains are USEFUL as INDEX FOSSILS, even if they cannot be used in this way
  • the PRESENCE OF PRESERVED POLLEN GRAIN IN SOIL OR ROCK SAMPLE CAN ENABLE TO CONSTRUCT A PICTURE OF THE TYPE/AMOUNT OF VEGETATION EXITING AT THE TIME THE DEPOSIT WAS MADE/LAID DOWN

An idea of climatic conditions prevailing at the time may be then worked out.
- this data can be used to confirm or refute relative dates arrived by other methods

33
Q

What are the conditions for fossils to be formed?

Why is the fossil record incomplete?

A

The fossil record is VERY INCOMPLETE AS CONDITIONS FOR FOSSILAITION DO NOT ALWAYS OCCUR, OR OCCURS AT IRREGULAR PERIODS OF TIME.

  1. A QUICK BURIAL of the MATERIAL
  2. the PRESENCE OF HARDBODY PARTS
  3. an ABSENCE OF DECAY ORGANISMS
  4. A long period of STABILITY - the organisms needs to be left undisturbed
34
Q

Why are problems with fossil recods?

A

The fossil record is VERU INCOMPLETE AS CONDITIONS FOR FOSSILAITION DO NOT ALWAYS OCCUR, OR OCCURS AT IRREGULAR PERIODS OF TIME.

  1. Fossilisation is a CHANCE occurrence and there may be many GAPS in the fossil records because organisms have not been preserved.
    - all four conditions need to be met
  2. Very small proportion of the fossils that DO EXIST HAVE BEEN ACTUALLY DISCOVERED.
    - some burial is too deep in the ground to be found
    - in inaccessible places
    - others may have not been recognised as fossils
    - may have been inadvertently destroyed by HUMAN ACTIVITY SUCH AS AGRICULTURE or INDUSTRY
  3. Fossil dating can be problematic
    - Carbon dating techniques, material containing carbon must be present and can only be dated back to 60 000 yrs
    To date material older than this, the AGE of the fossil IS DETERMINED BY THE SEDIMENTS IN WHICH IT IS FOUND.
    EG. K-Ar dating relies on suitable material such as volcanic lava being present,
  4. Unusual to find an ENTIRE organism or the whole skeleton of an organism
    - particularly true of fossil of human ancestors
35
Q

Explain why it is unusual to find entire organisms?

how the problem is solved?

A

Unusual to find an ENTIRE organism or the whole skeleton of an organism
- particularly true of fossils of human ancestors

Often a few fragments of bone, are used to construct what the organism may have looked like.

eg. Homo ergaster, found in Kenya
- fragments dated back to approx 1.8 million yrs ago
- pieced together like a jigsaw puzzle
- areas shown in black = bones missing of skull

Experts have estimated the shape of the face and upper jaw in order to complete the reconstruction
- such reconstructions are only approximations based on the experience of the scientists involved

  • other scientists may disagree with the interpretation and can lead to considerable controversy

The only resolution to such disagreements is to find more fossils
- but chances of finding = never slim

36
Q

How does the anatomy of fossils provide info for evolution?

A

Fossil evidence and current observations can provide info about the anatomy of organisms

  • to compare the structural features of related animals to ascertain a degree of similarity between them
  • similarities in structure often suggest that species have a common ancestor
37
Q

In comparative anatomy, what 3 areas does it focus and compare on? EXPLAIN THEM

A
  1. Embryology - comparing the very early stages of development of organisms
  2. Homologous structures - structures that are similar in structure but used in different ways
  3. Vestigial organs - structures that may once have been important but have LOST OR CHANGED THEIR FUNCTION
38
Q

Explain embryology

A

Comparative embryology provides evidence for evolutionary change over time by comparing the early stages in the development of organisms

  • although it is relatively easy to distinguish between the adults of different species
  • it is FREQUENTLY FAR MORE DIFFICULT TO TELL THE DIFFERENCE BETWEEN EMBRYOS
39
Q

Explain comparative emryology in vertebrates
human, chick

Other examples

A

In, vertebrates, comparing embryonic stages reveals remarkable similarities between the species at different times.

At one point in their development, THE EMBTOYS OF HUMAN and CHICKENS =
- slits and arches in their neck which are similar to gill slits and arches in fish
but they do not develop into gills
- SIMILARITIES INDICATE A COMMON ANCESTOR

OTHER EXAMPLES - striking evidence for common ancestors with later evolution along different pathways

  • Common features to vertebrae embryos at on stage =
    1. presence of a TAIL
    2. 2-CHAMBERED HEART
    3. SIMILAR BRAIN DEVELOPMENT
40
Q

Explain homologous structures

A

The degree of similarity in bone
In every case the BONES are ARRANGED IN A SIMILAR WAY - EVEN THOUGH SOME HAVE DEVELOPED DIFFERENT FUNCTIONS

Organisms possessing a homologous structure = have a common ancestor

41
Q

Explain forelimbs as a homologous structure

A

Forelims of vertebares

  • the same bone appears in various forms throughout the vertebraes:
    eg. feet of amphibians and replies, the wings of bats and birds, the left of a horse, the flipper of a whale or seal, and the human hand
  • similarity with the bones

These forelimb bones are described as HOMLOGOUS STRUCTURES because they POSSES A SIMILAR STRUCTURE.

THEREFORE THE ARRANGEMENT OF BONES IN FORELIMB IN SUCH A RANGE OF VERTEBRATES IS CONVINCING THAT THEY HAVE ALL EVOLVED FROM A COMMON ANCESTOR.

42
Q

Explain anthropoids

A

Anthropoids - human-like primates show a great many anatomical resemblances

  • the number of traits shared and the degree of similarity between the similar traits is remarkable, especially considering the range of habitats occupied.
43
Q

Explain Vestigial structures

A

Vestigial structures are structures that have changed during evolution to the point THEY NO LONGER FULFIL THEIR ORIGINAL FUNCTION

  • common in vertebrae species

Humans have as many as 90 of these structures

  • they are LARGELY FUNCTIONLESS WHEN THEIR ORIGINAL IS BEING CONSIDERED
  • HOWEVER, SOME RETAIN LESSER FUNCTIONS OR DEVELOP NEW ONES
44
Q

List some Vestigial organs

A
  1. Niciating membrane
  2. muscles that move external ears
  3. 3rd molars
  4. Muscle above the pubic bone
  5. coccyx
  6. nipples on the chest in males
  7. muscles in the base of hairs
  8. appendix
45
Q

Explain the nictitating membrane

A

or transparent 3rd eye

  • found in cats, birds, frogs and other vertebrae
  • able to cover the eye for protection

In humans, it is only represented by a PINKISH MEMBRANE LOCATED AT THE INNER CORNER OF EACH EYE THAT IS UNABLE TO COVER THE EYE

Hence - cannot fulfil its original function
however, does has some use in maintaining TEAR DRAINAGE.

46
Q

Explain muscles in external ears

A

The muscles in the external ears that move them are found in many mammals

  • reduced to an extent in humans
  • most individuals cannot move their ears at all
47
Q

Explain 3rd molars

A

Wisdom teeth

  • erupt abnormally and cannot be used in mastication
  • frequently are removed before eruption so they do not become painful
  • about 1/5th of the population is spared any discomfort because they do not develop
48
Q

Explain muscle live above the pubic bone

A

1/5th of the population do not develop the muscles that lie above the pubic bone - CALLED THE PYRAMIDALIS MUSCLES

  • these muscles, if present do not make any difference to muscular performance
49
Q

Explain tails in humans

A

Humans still have the vertebrae for a tail, fused to form COCCYX

50
Q

Explain the male nipples

A

males have nipples on their chest

  • some would argue these should not be termed vestigial, as they had no function in the fist place
  • they appear to be retained in males because all human foetuses develop from the same basic genetic from, and nipples do have an important function in females
51
Q

Explain muscles at the base of hairs

A

are considered to be vestigial organs
- in mammals with fur or spines and in birds with feathers - these are tiny muscles that pull the hair/feather upright, creating a layer of insulating air to protect against the cold.

  • human hair is so fine that it is not capable of such function and the contraction of the muscles is seen as GOOSE BUMPS
52
Q

Explain the appenidx

A
  • commonly considered a vestigial structure
    in herbivorous vertebrates, the appendix plays a role in the digestion of tough plant matter
  • thought to have a similar role in ancient humans, - whose diet was more plant-based
  • due to change of dier to more easily digestible food - appendix is no longer needed for the original function
  • many have their appendix removed following inflammation known as appendicitis
  • do not appear to have any negative effects upon its removal
  • research indicates the appendix has a role in the immune system-producing and strong god gut bacteria

based on this info there’s is debate on whether or nor it is an vestigial organ

53
Q

WHY DO VESTIGIAL ORGANS EXIST?

A

Evolutionary mechanisms can be sued to explain the existence of many of these structures which appear to have no function.
- they are what remains of organs that ere functional in ancestral forms

overtime and with changing environments; conditions, such organs were no longer essential to survive
hence were gradually reduced to vestigial remains.
- not harmful in any way,

NATURAL SELECTION has REDUCED THE ORGANS NON-FUNCTIONAL REMANNST BECAUSE IT WOULD HAVE BEEN A WASTE OF ORGANISMS ENERGY AND RESOURCES TO MAINTAIN USELESS STRUCTURES.

SUCH ORGANS WILL PROBABLY DISAPPEAR ALTOGETHER AS THERE IS NO SELECTION PRESSURE TO RETAIN THEM

54
Q

What is a phylogenetic tree?

A

dendrogram
represents the evolutionary relationships between a number of organisms derived from a common ancestor.

  • often used to simplify complex relationships, in order to enable them to be easily understood more
  • useful for representing relationships as well as organising knowledge of genetic diversity and structural classifications
  • particularly useful in showing evolutionary pathways and have been used as such since the time of Charles darwin
  • only ‘inferred relationships’ and interpretation of data
55
Q

Steps in producing dendrograms

A
  1. identify species with the most similarities
    - draw these joined by short branches showing a recent common ancestor
  2. identify the species with the next most
    (incomplete)

ALL SPECIES THAT LIVE IN THE PRESENT ARE DRAWN LEVEL WITH EACH OTHER
IF THE SPECIES WAS EXTINCT THE BRANCH WOULD END LOWER DOWN

AN AXIS IS DRAWN TO SHOW THE PROGRESS OF TIME

Human Biology: Unit 4 (7 decks)

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