what is biological evolution
the process by which present life forms have arisen from life forms that have existed in the past
difference between a theory and a hypothesis
a theory is an explanation for an observable phenomenon that is supported by facts ,models and laws. a hypothesis is a suggested explanation for an observable phenomenon that predicts a possible outcome
what is the theory of evolution
it is a scientific theory since various hypothesis of evolution have been tested and verified over time
what are the four evidences of evolution
-genetics
-fossil records
-modification by descent
-biogeography
why is fossil records an evidence of evolution
-fossils records provide evidence for life forms that have existed in the past or a extinct
-intermediate forms of fossils indicate the changing forms of plant and animals
how to prove that a species has a common ancestor using genetics
if they have a similar sequence of genes, metabolism processes ,identical protein synthesis and DNA structure , they have a common ancestor
what is modification by descent
it is when organisms transfer genetic characteristics from one generation to the next
how is a gene pool formed
- two genes combine during fertilization in sexual reproduction
- a gene or chromosomal mutation occurs
- these variations lead to modified hereditary material being passed from parent to child
- this is called descent with modification
- ## genes found in a pool are constantly changing and modified genes are formed
what is biogeography
it is when different but closely related species in similar biomes have similar feacture.in adapting to that biome, indicate that they probably developed from a common ancestral species.
why are they gaps in the fossil records
only few organisms are preserved as fossils because they need to be covered soon after death otherwise they will be decomposed by bacteria
only organisms with a solid and resistant skeleton are easily preserved
not all fossils have been discovered on earth
what is a biological species
a group of organisms that can interbreed and produce fertile offspring
population
a group of organisms of the same species living in the same habitat
what are the 4 sources of variation
meiosis
- crossing over during prophase 1
-random arrangement of chromosomes during metaphase
gene mutation
chance fertilization
theory of Lamarckism
law of disuse and use
- the environment gives rise to changes in the environment
- the use of a structure causes it to enlarge or become more developed
-repeated disuse of a structure causes it to degenerate or become less developed
law of inheritance of acquired characteristics
- the modification of an organism acquired during its lifetime can be passed on to its offspring
why Lamarck theory was rejected
- acquired characteristics are not inherited
- organisms did not evolve because they want to evolve
- Lamarck believed in determinization which is the internal drive for organisms to change
Darwin’s theory of natural selection
- there is a great deal of variation amongst offspring
- some have favorable characteristics while others do not
- when there is a change in the environment or competition
- the organisms with the favorable characteristics will survive while the organisms with the unfavorable characteristics will die off
- the organisms that survive reproduce and pass on the allele for the favorable characteristic to their offspring
- the next generation will therefore have a higher proportion of organisms with the favorable characteristics
definition of punctuated equilibrium
long periods with little or no change and then short periods of rapid change through natural selection during which new species form
artificial selection
- humans determine which characteristics should be selected
- suitable characteristics are chosen by the breeder or the farmer
natural selection
characteristics that are selected are those that are best suited to the environmental conditions
speciation through geographical isolation
- a population of a single species is separated by a geographical
barrier - the population splits into two
- there is now no gene flow between the two populations
- each populations is exposed to different environmental conditions
- natural selection occurs independently in each of the populations
- such that the two populations become different genotypically and
phenotypically - even if the two populations were to mix again ,they will not be
able to interbreed - the two populations are now different species
what are the five reproductive isolation methods
- breeding at different times of the year
- species specific courtship behavior
- plant adaption to different pollinators
- infertile offspring’s
- prevention of fertilization
examples of natural selection and evolution
- use of insectides and consequence resistance to insectides in insects
- development of resistant strains of tuberculosis- causing bacteria to antibiotics due to variations in bacteria and failure to complete antibiotic courses
- HIV resistance to antiretroviral medication
- beak and body size of Galapagos finches
similarities between homosapiens and apes
(sense of smell)
(vision)
(arms)
(hands)
(walking)
(foramen magnus)
(sex)
(cranium0
- reduced sense of smell
- binocular vision
- eyes with cones(color vision)
- freely rotating arms
- elbow joints allowing rotation of movements
- flat nails instead of claws
- opposable thumbs
- bipedal
- foramen magnus in a more forward position
- sexual dimorphism
- longer upper arms
- large brains
- five digits per fingers
- parts of the brain that process information from the hands and the
eyes are enlarged
characteristics of homo sapiens
(cranium)
(brow ridges)
(spine)
(pelvis)
(canines)
(jaws)
(palate shape)
(dentition)
(cranial ridge)
(foramen magnus)
- large cranium
-brow ridges not well developed - more curved(s shaped) spine
- short wide pelvis
- small canines
- small and circular palate shape
- small jaws
- less prognathous jaws
- no cranial ridge
- foramen magnus in a more forward position
- small gaps between teeth
