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Diversity IEB & DBE life sciences grade 12 notes

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  • Course
  • Life Sciences
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  • 12th Grade

This set of notes contain a detailed explanations on the diversity containing the following: Origin of an idea about origins Scientific theory of evolution Modification by descent, comparative anatomy Evidence from Biogeography Evidence from Comparative Embryology Graphical Representation ...

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  • May 18, 2024
  • 25
  • 2022/2023
  • Class notes
  • Dk
  • All classes

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  • matric life sciences notes exam prep

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  • 12th Grade
  • Life Sciences
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Diversity

, Origin of an idea about origins
Diversity
Terms and definitions
Population: a group of individuals of same species that form a breeding unit & occupy same
habitat at same time.
Evolution: process by which characteristics of a population change over time, first living
organisms somehow gave rise to organisms that exist today.
Belief: an explanation for a phenomenon that is based on religious/cultural values, not usually
supported by scientific evidence.
Hypothesis: a possible, or temporary explanation of a phenomenon, that can be tested using
observations and/or experiments. Depending on the results, it is rejected or accepted.
Theory: a widely held explanation of a phenomenon that is supported by numerous observations,
experiments and scientific evidence.
Paleontology: the study of fossils.
Archaeology: Study of things that are very old.
Anthropology: Study of natural history & development of humans.
Fossils: preserved remains/traces of organisms that once lived on Earth.
Extant: Still living today
Scientific theory of evolution
Fossil records as evidence of ancient life
Recording the position of fossils in geological strata, paleontologists deduce their relative age.
Oldest rock strata are found deepest in the earth, youngest rocks occur near the surface.
Fossils found in the deeper strata lived on Earth longer ago than those fossilised in younger strata.
Relative dating and radiometric dating are more accurate.
Relative dating, relating to age of another fossil or geological event (volcanic eruption), tell
whether fossil was formed before another fossil/geological event; not exact age of a fossil.
Radiometric dating, finding out how much of a radioactive substance in a fossil has changed
to form another substance (Radioactive C14 slowly decays & becomes Nitrogen 14).

, Modification by descent, comparative anatomy
Evolutionary scientists compare anatomy of fossils & skeletons of living species, to
identify trends in the adaptations of bones to suit particular functions.
Homologous structures
Forelimbs of different mammals adapt to ecological
niches. Eg, pentadactyl limb.
Mammals have same basic forelimb structure,
ending in five digits, one large bone attached to
smaller bones, attached to several small bones,
attached to approximately five digits.
Charles Darwin interpretation of the structural differences of forelimbs of mammals:
Forelimbs arose from a common ancestor, had same basic plan.
These structures show variations, modified to perform different functions (fly, dig, run, swim)
eg. of divergent evolution: species evolve from a common ancestor, share similar characteristics
Analogous structures
Features appear to have similar functions but have
evolved in different ways.
Eg of convergent evolution: organisms are not closely
related evolve similar adaptations independently
Vestigial/rudimentary structures & organs
Evolution causes the change or loss of structures once
useful to ancestors of an organism, but are no longer
useful in current environment/body plan.
Vestigial structures: small, poorly developed structures
inherited from common ancestor but have no real use,
(eg, human appendix, whale & snakes pelvises)

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