Chapter 14 - 17History of Biological Diversity

Preserved evidence of organism Learned different types of fossils

◦ Molds, casts, petrified fossils, animal & plant remains & trace fossils

◦ Geologic time scale – eras, periods◦ Relative age of rocks – half -life

Carbon-14 dating

Fossils:

Hereditary changes in groups of living organisms over time

Theory of Evolution:

Anatomy – study of structure◦ If the diverged from a common ancestor they have

similar characteristics (homologous structures) > the # of shared structures btw 2 species, the more

closely related they are◦ Vestigial organs (little or no function to the

organism) are often homologous w/ structures in related species that still work

◦ Species living in diff locations under similar ecological conditions, dvlp similar structures & behaviors If conditions change, those w/ favorable anatomical

traits become established

Scientific Areas that have contributed to this theory:

Embryology – embryonic dvlpt or organisms◦ Looks @ pre-birth, pre-hatching, or pre-

germination

◦ Can see similarities not seen in adults b/c adults change form

◦ Similar embryonic structures means common ancestry

Biochemistry – genes & proteins◦ More similar the DNA & amino acid seq, the more

likely they are to have a common ancestor

◦ Better than anatomy When species are so closely related they don’t

appear to be diff When species are so diverse they share few similar

structures

Paleontology – prehistoric life◦ Fossil record gives evidence of life forms & envir

◦ Supports evolutionary relationships Shows a pattern of gradual change

◦ Not complete – gaps

◦ The older the fossil, less resemblance to modern version

Defined as the evolutionary history of a species or a grp of related species

Dvlpd evolutionary theory that states that all forms of life on Earth are related b/c there is a common ancestor

From all of this comes---- Phylogeny!

Anatomy – similarity means a common ancestor◦ Divergence – acculum. of evolutionary differences

May be homologous in structure but not function◦ Convergence – structures w/ diff evolutionary

histories become more similar over time to adapt to a similar envir (analogous structures)

Embryology – highly divergent taxa (grps) w/ so many anatomical diff◦ ontogeny (growth & dvlpt of an indiv organism) will

recapitulate phylogeny

Common Ancestor????

Paleontology – gives info on dates & order of divergence◦ Transitional fossils – show links in traits btw grps for

documenting intermediate stages of a species’ evolution

Biochemistry – molecular clock - > the genetic similarity, more recent is the common ancestor

***1 piece of evidence doesn’t give an accurate pic of the evolution of 1 species – evidence from all the fields gives more reliable info

Phylogenetic Tree

Cladogram

Hard to classify b/c species are becoming extinct

Most recent classification:◦ 3 Domains – Domain Archae, Domain Bacteria,

Domain Eukarya◦ 6 Kingdoms – Kingdom Eubacteria,

Kingdom Archaebacteria, Kingdom Protista, Kingdom Fungi, Kingdom Plantae, Kingdom Animalia

Classification:

All the changes that have transformed life on Earth

Can occur on a small scale affecting a single population (microevolution) or large scale affecting species across populations (macroevolution)

Biological Evolution

Occurs b/c indiv of a pop have diff traits that allow them to be more or less effective in an envir than other members

Changes in inherited traits over time – increases a species’ “fitness” in its envir.

Natural Selection:

1. Overproduction of Offspring: ◦ raises the chance that some will survive but also

inc competition for resources

4 Main Principals of Natural Selection:

2. Variation: ◦ exists w/in the inherited traits in the phenotypes

(which is controlled by the genotypes & the envir)◦ All life that has ever existed on Earth, share @

least nucleic acids (DNA or RNA) and proteins◦ 2 types of reproduction:

Sexual – meiosis creates gametes, fertilization takes place creating variation

Asexual – 1 parent that produces a clone (binary fission or mitosis) – ex.) budding, fragmentation & vegetative propagation – repro rate is higher but in a changing envir can’t adapt

If you could reproduce sexually & asexually, better advantage for survival!!!!

3. Adaptation: ◦ increased frequency of a particular structure,

physiological process or behavior in a pop that makes it better able to survive & reproduce

◦ Gene pool changes over time b/c those less adapted will die

◦ “fitness” – measure of how a trait contributes to repro success

SURVIVAL OF THE FITTEST!!!!

4. Descent w/ Modification: ◦ as the envir of a pop changes, the entire process

of natural selection yields pop w/ new phenotypes

◦ over time pop will have diff structures, live in diff niches or habitats than ancestors

Species – grp of organisms that share similar characteristics & can interbreed w/ 1 another to produce fertile offspring

Means they share a common gene pool (all genes of all the indivs in a pop)

So a genetic change in 1 indiv can spread through a pop through mating◦ If the change inc fitness, then more indiv will have

it

Diversity w/in the Species:

So the greater the diversity, the greater the chances for the species to survive

Favorable traits in male & female organisms enhance repro. success◦ Non-random mating changes the gene pool over

time & a better adapted species

Inherited beneficial traits become more prevalent, & detrimental traits become less

Genetic Drift – random change in allele frequency◦ Rare alleles dec in freq & are eliminated◦ Other alleles inc & become fixed◦ Seen more in small pop vs large pop

Gene Flow – movemt of genes in & out of a pop – due to migration

Non-random Mating – limits the freq of some alleles

Factors That Influence Genetic Variability:

Mutations – inc freq & types of allele changes in a pop

Natural Selection – allows most favorable phenotypes to survive & be passed on

When there is no change in allele freq, pop is in genetic equilibrium

5 conditions:◦ Large population◦ No movement in or out of pop◦ Random mating◦ No mutations◦ No natural selection

Hardy-Weinberg Principle:

Process of forming a new species by biological evolution from a pre-existing species

Usually a result of isolation (reproductive or temporal, behavioral, geographic)

As different traits become favorable the 2 pop gradually become so different they are unable to reproduce w/ each other

Speciation:

Gradualism – slow changes over a period of time

Punctuated Equilibrium – periods of abrupt changes after periods of little change

Adaptive Radiation/Divergent Evolution - # of different species split off from a common ancestor – survive in different niches

Convergent Evolution – occur among different species living in similar envir – produce analogous structures

Patterns of Evolution:

Coevolution – 2 or more species living in close proximity change in response to each other

Extinction – elimination of a species b/c they can’t adapt – can be gradual or rapid◦ Gradual Extinction – slow rate due to other

organisms, changes in climate or natural disasters◦ Mass Extinction – result of catastrophic events

that change the envir very suddenly