HOMOLOGOUS STRUCTURES
(Modification by Descent)
Evolutionary scientists compare the anatomy of fossils and skeletons
to identify trends
in the adaptations of bones to suit particular
functions.
What does homology suggest evidence for
evolutionary linkages between groups
* they descended from a common ancestor
Homologous structures
Homo = same
Body parts similar in structure but Defn
have different functions
what is Biogeography
Biogeography is the study of the geographical distribution of biological organisms
What does biogeography provide evidence for
- evolution when continental drift is considered
eg. mesosurarus must have evolved before Gondwana split - also provides evidence that many modern species have evolved from a common extinct ancestor
eg. Current distribution of different species of flightless birds in the southern hemisphere continents suggests that they may have evolved before Gondwana split
What does the effect pf continental drift on biog. provide
evidence for evolution of ancient species
GENETIC evidence for evolution
- Suggests that “organisms have
descended from a common ancestor”.
- All forms of life: RNA + DNA same 4 nucleotides (A, C, G, T / U)
- Proteins same 20 amino acids different combinations + sequences all organisms
- Same genetic code is used to make identical proteins in all organisms - Suggests the “degree of relatedness between organisms”.
- The more amino acid or DNA sequences shared, the closer the relationship - the more recently they have diverged from a
common ancestor.
* The fewer sequences shared, the more distant the relationship further in the past that the species diverged.
What is variation
differences in the genotype and phenotype amongst individuals of a particular species
What contributes to variation?
CROSSING OVER
RANDOM ARRANGEMENT
RANDOM FERTILISATION
MUTATION
RANDOM MATING
Types of variation?
- Discontinuos
- variation that occurs as discrete classes ( separate thus no range )
eg. blood type; beetle carapace colour
- characteristics are controlled by a single gene
- Continuous
- phenotypes determined by multiple genes
eg. height; weight; skin colour
- phenotypes determined by multiple genes
LAMARCK
( believed that organisms had the ability to change their appearance and that these characteristics would also occur in their offspring)
2 Laws:
* Use & Disuse
- if certain organs were used MORE they would increase in SIZE or EFFICIENCY.
If organs were not used they would get smaller and eventually disappear
* Inheritance of ACQUIRED characteristics
- These physical changes or characteristics (brought about by use or disuse) which were acquired during their lifetime could then passed on to their offspring
- Reasons for their REJECTION
- NO EVIDENCE TO SHOW THAT CHANGES BROUGHT ABOUT BY ADAPTATION TO ENVIRONMENT ARE INHERITED FROM PARENT
TO OFFSPRING.
- NO EVIDENCE TO SHOW THAT CHANGES BROUGHT ABOUT BY ADAPTATION TO ENVIRONMENT ARE INHERITED FROM PARENT
- NO EVIDENCE THAT STRUCTURES USED MORE OFTEN BECOME MORE DEVELOPED.
- NATURE ALLOWS ORGANISMS TO CHANGE AND NOT BECAUSE ORGANISMS WANT TO CHANGE
DARWINISM
- Proposes that LIVING ORGANISMS EVOLVE:
gradually from common ancestors
MORE DETAIL LATER by NATURAL SELECTION
Those that did not evolve ….. DIED - extinct - Many expeditions on ship HMS Beagle
- Darwin eventually wrote his now famous book, The Origin of Species by Natural Selection, published in 1859.
PUNCTUATED EQUILIBRIUM
- Proposed by: GOULD & ELDRIDGE Focuses on the PACE OF EVOLUTION new species
- Theory is supported by absence of transitional fossils.
- Contrary to Darwin’s theory of Gradualism, PUNCTUATED EQUILIBRIUM proposed
DARWINISM GRADUALISM
Proposed that MANY SMALL changes over LONG periods of time
resulted in new species
PUNCTUATED
EQUILIBRIUM
Proposed that new species resulted RAPIDLY during SHORT periods of time
alternating with LONG periods of NO CHANGE
