3.2 - 3.4: evolution

Chapter 8: evolution

Evolution

gradual change of characteristics within a population, producing a change in species over time ; Driven by process of natural selection

Who was the first to explain natural selection as a driving force and lay evidence for evolution?

Charles Darwin

Carolus linnaeus

well known botanist who speculated on the origin of relationships between groups of species in the mid 1700s

Lamrack

• French scientist that proposed that organisms acquire traits over their life span that equip them to survive within their environment and pass those traits on to their offspring 

  • Presented the idea that giraffes developed longer necks during their lifespan from efforts to reach high branches, passing longer necks onto their children.

  • His theory was discredited 

Darwinian concept of natural selection

• Population growth and maintenance of a species is dependent on limiting factors 

• Individuals within the species that are unable to acquire the minimum requirement of resources are unable to reproduce 

• Organisms are only able to support a limited number of organisms, known as the carrying capacity (usually designated by the letter K) 

• Once the carrying capacity (K) is reached, a competition for resources ensues 

• Individuals who win the competition pass their traits on to the next generation

• Traits providing the competitive edge will be represented most often in succeeding generations

Gene pool

the entire collection of genes within a given population ; Individuals in the population will have only 1 pair of alleles for a particular single-trait gene, Yet the gene pool may have dozens of alleles for this trait

Evolution does not occur through changes from individual to individual, but rather as _____

the gene pool changes through one of a number of possible mechanisms

Differential reproduction

one mechanism that drives the changing of traits in a species over time ;

• Individuals within a population that are the most adapted to the environment are also the most likely individuals to reproduce successfully

• Reproductive processes tend to strengthen the frequency of expression of heritable traits across the population 

• Differential reproduction increases the number of alleles for desirable traits in the gene pool 

Genetic drift

• Over time a gene pool (particularly in a small population) may experience a change in frequency of particular genes simply due to chance fluctuations

• Genetic drift has no particular tie to environmental conditions  and thus the random change in gene frequency is unpredictable 

• Genetic drift actually causes a reduction in genetic variation

• Occurs within finite separated populations, allowing that population to develop its own distinct gene pool 

Gene migration

• Occasionally an individual from an adjacent population of the same species may immigrate and breed with a member of the previously locally isolated group

• Introduction of new games from the immigrant results in a change of the gene pool

•  also occasionally successful between members of different, but related, species; the resulting hybrids succeed in adding increased variability to the gene pool

Hardy-Weinberg law of equilibrium

Study of genetics shows that in a situation where random mating is occurring within a population (which is in equilibrium with its environment) gene frequencies and genotype ratios will remain constant from generation to generation

p + q =1

p2 + 2pq + q2 = 1

Species

an interbreeding population that shares a common gene pool and produces viable offspring

What are the 2 mechanisms that produce seperate species

allopatric speciation and sympatric speciation

What prohibits different species from interbreeding

In order for a new species to develop, substantial genetic changes must occur between populations

Allopatric speciation

• occurs when 2 populations are geographically isolated from each other 

  • Ex: species of squirrels separated by an event such as a volcanic eruption. These 2 populations will continue to reproduce and experience genetic drift and/or mutation over time 

  • Species experience too much change to allow them to successfully interbreed again (resulting in the production of 2 different species) 

sympatric speciation

• when a population develops members with a genetic difference, which prevents successful reproductions with the original species 

  • The genetically different members reproduce with each other, producing a population which is separate from the original species,

Adaptive radiation

• when some members of a species move into new geographic areas looking for resources or to escape predators

• In this case a natural event does not separate the population, instead the population moves 

• Over time the species will specially adapt to live more efficiently in the new environment 

• Through this process a single species can develop into several diverse species over time 

punctuated equilibrium

• speciation events interspersed with periods of relative stasis

• Actual Fossil record seems to show that organisms in general survive many generations with very little change over long periods of geologic time 

• New species appeared in the fossils suddenly, without transitional forms 

• Punctuated equilibrium is still not fast. It happens on the scale of tens or hundreds of thousands of years

Polymorphism

genetic variation carried by members of a species for a given trait ; Gender is an example of dimorphism (2 variations in most mammalian species)

Evolutionary mechanisms exist that tend towards a balanced polymorphism in order to keep any particular version within a species from dominating unless ____

that version is more suited for its ecological niche

Heterozygote advantage

• one mechanism whereby polymorphism is maintained. Having 2 different alleles for a given phenotype is a positive trait for survival in many instances 

  • Ex: with sickle cell disease the homozygous trait is deadly but the heterozygous trait is advantageous, therefore the heterozygous trait is favored, selected, and retained in the population 

 frequency dependent selection

an evolutionary process by which the fitness of a phenotype or genotype depends on the phenotype or genotype composition of a given population.

Oparin hypothesis

theory regarding the origin of life that proposed that Earth was 4.5 billion years old, and that life came from Earth’s “primordial soup” that allowed molecules to develop into proteins and then into cells

__ provided support for Oparin’s hypothesis in experiments where he exposed simple inorganic molecules to electrical charges similar to lightning

Stanley Miller

Sidney Fox

major evolution researcher of the 1960s, conducted experiments that proved ultraviolet light may have induced the formation of dipeptides from amino acids

Cyril Ponnamperuma

• demonstrated that small amounts of guanine formed from the thermal polymerization of amino acids

  • He also proved the synthesis of adenine and ribose from long-term treatment of reducing atmospheric gases with electrical current

What happened in early Earth once organic compounds had been synthesized?

primitive cells most likely developed that contained genetic material in the form of RNA that used energy derived from ATP. these primitive cells were Prokaryotic and similar to some bacteria now found on Earth

endosymbiont theory

• suggests that original prokaryotic cells took in other cells that performed various tasks 

  • For ex: an original cell could have absorbed  several symbiotic bacteria that then evolved into mitochondria. Several cells that lived in symbiosis would have combined and evolved to form a single eukaryotic cell 

How did the evolution of plant species begin?

considered to have begun with heterotrophic prokaryotic cells

Why were early cells Anaerobic?

because the Earth atmosphere was (presumed to be) lacking oxygen

How did early Earth get oxygen into its atmosphere?

Over time some bacteria evolved the ability to carry on photosynthesis (cyanobacteria) thus becoming autotrophic, which then introduced significant amounts of oxygen into the atmosphere

How did the formation of Oxygen in early Earth’s atmosphere lead to the creation of a new niche?

Since oxygen is poisonous to most anaerobic cells, a new niche opened up: cells able to not only survive in the presence of oxygen, but also able to use it metabolism

How did Cyanobacteria evolve into Eukaryotic cells & then into plants?

Cyanobacteria were incorporated into larger aerobic cells, which then evolved into photosynthetic eukaryotic cells ; Cellular organization increased, nuclei and membranes formed, and cell specialization occurred, leading to multicellular photosynthetic organisms (plants)

The earliest plants were ___

aquatic

How did plants become terrestrial?

cell walls thickened, and tissues to carry water and nutrients developed ; As plants continued to adapt to land conditions, differentiation of tissues continued, resulting in the evolution of stems, leaves, roots, and seeds; Development of the seed was a key factor in the survival of land plants

Where did the evolution of animals begin?

Thought to have begun with marine protists (animal cells have the most similarity to marine protist cells)

Homologous structures

structures that exist in 2 different species because they share a common ancestry

Analogous structures

structures that are similar because of their common function, but do not share a common ancestry

What did humans evolve from?

Humans are thought to have evolved from primates who, over time, developed larger brains

Homo erectus

• Oldest known fossil of the human genus

• Thought to be 1.8 million years old

• About the size of a modern human brain

• Thought to walk upright and have facial features more closely related to humans than to apes

How do ecological conditions relate to evolution?

They affect (if not determine) the course of evolution of species in a particular area

Life history strategies

 characteristics that differentiate organisms and how well they are suited to live in an ecosystem; 2 types of life history strategies; opportunistic & equilibreal

Opportunistic life history strategy

• Also known as r-selected

• Tend to be pioneer specie in a new or recently devastated community 

• Traits that allow them to succeed in the long term and traits that help make them succeed in a new / changing environment

• Tend to have short maduration times and overall short lifespans 

• High mortality rates

• Often have asexual reproduction with high numbers of offspring 

• Do not parent their young 

• Rapidly reproducing species that are also easily wiped out y more sophisticated population that follow

• Ex: dandelions 

equilibreal life history strategy

• Also known as k-selected

• Organisms that overtake the opportunistic pioneer species

• Tend to have long lifespans with a long maduration time and corresponding low mortality rate

• Reproduce sexually and produce fewer (longer living) offspring that they tend to parent 

• Tend to stay within their established borders rather than dispersing

• Dominate in various ecosystems

• Ex: oak tree

Kin selection

the tendency of an individual to be altruistic toward a close relative, resulting in the preservation of its genetic traits

Taxonomy

study that seeks to organize living things into groups based on morphology, or genetics

homonid fossils

• Australapitthocus afarensis (lucy) - 4.5 mil years ago, head smaller, long arms

• Homo erectis- first from same genus, 1.8 mil yrs ago, head larger, facial features

• First homo sapiens (cro-magnon man) - 100,000 years ago, looked like us

Australapitthocus afarensis (lucy)

Ancestor of homo sapiens; 4.5 mil years ago, head smaller, long arms

Homo erectis

ancestor of homo sapiens; first from same genus, 1.8 mil yrs ago, head larger, facial features

cro-magnon man

First homo sapiens ; 100,000 years ago, looked like us

Cambrian explosion

•  rapid increase in multicellular organisms

  • Aquatic plants appeared

  • More major animal phyla appeared

  • New niches evident: active hunting, burrowing into sediment, making branching burrows 

Who first developed the current methods on taxonomy?

Carolus Linnaeus published Systema Naturae book in 1735, first developed current methods of taxonomy

What did Linnaeus base his taxonomic keys on?

based his taxonomic keys on the morphological (outward anatomical) differences seen among species ; Used 2 latin categories: genus & species to name each organism

taxonomic classifications

Every species belongs to a genus, family, order, class, phylum, and kingdom

How many domains does the modern classification system contain?

The Archaea, the Eubacteria, and the Eukaryota

Archaea

• prokaryotic, have unique RNA, and are able to live in the extreme ecosystems on Earth 

  • Includes methane producing organism and organism able to withstand extreme temperatures and high salinity 

Eubacteria

contain the prokaryotic organisms we call bacteria

Eukaryota

4 major kingdoms; Includes all organisms that possess eukaryotic cells 

What are the 4 major kingdoms of the domain Eukaryota ?

Protista, fungi, animalia, and plantae

What are the 9 major phyla within the kingdom animalia?

• Porifera - the sponges

• 2. Cnidaria - jellyfish, sea anemones, hydra, etc.

• 3. Platyhelminthes - flat worms

• 4. Nematoda - round worms

• 5. Mollusca - snails, clams, squid, etc.

• 6. Annelida - segmented worms (earthworms, leeches, etc.)

• 7. Arthropoda - crabs, spiders, lobster, millipedes, insects

• 8. Echinodermata - sea stars, sand dollars, etc. 

• 9. Chordata - fish, amphibians, reptiles, birds, mammals, lampreys 

Porifera

kingdom animalia of the phyla of the sponges

Cnidaria

jellyfish, sea anemones, hydra, etc.

Platyhelminthes

flat worms

Nematoda

round worms

Mollusca

snails, clams, squid, etc.

Annelida

segmented worms (earthworms, leeches, etc.)

Arthropoda

crabs, spiders, lobster, millipedes, insects

Echinodermata

sea stars, sand dollars, etc. 

Chordata

fish, amphibians, reptiles, birds, mammals, lampreys 

Which phylum are vertebrates in?

the phylum chordata, which is slit into 3 subphyla: Urochordata (animals with a tail cord such as tunicates), the cephalochordata ( animals with a head cord such as lampreys), and the vertebrata (animals with a backbone)

Urochordata

Subphyla of the phylum Chordata; animals with a tail cord such as tunicates

cephalochordata

Subphyla of the phylum Chordata; animals with a head cord such as lampreys

vertebrata

Subphyla of the phylum Chordata; animals with a backbone

What are the 2 superclasses of the subphylum vertebrata?

the aganatha (animals with no jaws) and the gnathostomata (animals with jaws)

aganatha

animals with no jaws

gnathostomata

animals with jaws

What are Gnathostomata’s 6 classes?

1. Chondrichthyes - fish with a cartilaginous endoskeleton, two chambered heard, 5-7 gill pairs, no swim bladder or lung, and internal fertilization (sharks, rays, etc)

2. Osteichthyes - fish with a bony skeleton, numerous vertebrae, swim bladder (usually), 2 chambered heart, gills with bony gill arches, and external fertilization (herring, carp, tuna)

3. Amphibia - animals with bony skeleton, usually with 4 limbs having webbed feet with 4 toes, cold blooded (ectothermic), large mouth with small teeth, 3 chambered heart, separate sexes, internal or external fertilization, amniotic egg (salamanders, frogs, etc.) 

4. Reptilia - horny epidermal scales, usually have paired limbs with 5 toes (except limbless snakes), bony skeleton, lungs, no gills, most have 3 chambered hearts, cold blooded (ectothermic), internal fertilization, separate sexes, mostly egg laying (oviparous), eggs contain extraembryonic membranes (snakes, lizards, alligators) 

5. Aves - spindle shaped body (with head, neck, trunk, and tail), long neck, paired limbs, most have wings for flying, 4-toed feet, feathers, leg scales, bony skeletons, bones with air cavities, beaks, no teeth, 4 chambered hearts, warm blooded (endothermic), lungs with thin air sacks, separate sexes, egg-laying, eggs have hard calcified shell (birds, ducks, sparrows, etc.)

6. Mammalia - body covered with hair, glands (sweat, scent, sebaceous, mammary), teeth, fleshy external ears, usually 4 limbs, 4 chambered heart, lungs, larnyx, highly developed brain, warm blooded, internal fertlization, live birth (except for the egg laying mono-tremes), milk producing (cows, humans, platypus, apes, etc.) 

Chondrichthyes

fish with a cartilaginous endoskeleton, two chambered heard, 5-7 gill pairs, no swim bladder or lung, and internal fertilization (sharks, rays, etc)

Osteichthyes

fish with a bony skeleton, numerous vertebrae, swim bladder (usually), 2 chambered heart, gills with bony gill arches, and external fertilization (herring, carp, tuna)

Amphibia

animals with bony skeleton, usually with 4 limbs having webbed feet with 4 toes, cold blooded (ectothermic), large mouth with small teeth, 3 chambered heart, separate sexes, internal or external fertilization, amniotic egg (salamanders, frogs, etc.)

Reptilia

horny epidermal scales, usually have paired limbs with 5 toes (except limbless snakes), bony skeleton, lungs, no gills, most have 3 chambered hearts, cold blooded (ectothermic), internal fertilization, separate sexes, mostly egg laying (oviparous), eggs contain extraembryonic membranes (snakes, lizards, alligators)

Aves

spindle shaped body (with head, neck, trunk, and tail), long neck, paired limbs, most have wings for flying, 4-toed feet, feathers, leg scales, bony skeletons, bones with air cavities, beaks, no teeth, 4 chambered hearts, warm blooded (endothermic), lungs with thin air sacks, separate sexes, egg-laying, eggs have hard calcified shell (birds, ducks, sparrows, etc.)

Mammalia

body covered with hair, glands (sweat, scent, sebaceous, mammary), teeth, fleshy external ears, usually 4 limbs, 4 chambered heart, lungs, larnyx, highly developed brain, warm blooded, internal fertlization, live birth (except for the egg laying mono-tremes), milk producing (cows, humans, platypus, apes, etc.)

Directional Selection

a type of natural selection that favors one extreme phenotype over the mean (average) phenotype in a population, causing the trait's frequency to shift in a specific direction over time

Disruptive selection

Type of natural selection where both extremes are selected; the median is not favorable in this case  Instead, it is desirable to have one extreme or the other, with no preference over which extreme is better for survival. 

Stabilizing selection

natural selection where The majority of the species fall somewhere in the middle of those two extremes. This creates a very large peak right in the middle of the bell curve. This is usually caused by a blending of traits through incomplete or codominance of the alleles.

taxonomic levels in order

Domain → kingdom → phylum → class → order → family → genus → species

King Philip Can Order Fried Goat Sometimes (way to remember taxonomic levels in order)

Kingdom, Phylum, Class, Order, Family, Genus, Species

Operant Conditioning

a learning process where voluntary behaviors are modified by their consequences.