BIOEE1780 Week 4

• It remains relatively pristine. No invasive species have been introduced. No farming has been done. Thus, it can confidently be said that there have been no anthropogenic extinctions on the island.
• It is ecologically simple; There aren’t many plant species and small numbers of finches are born every year.
• No finches emigrate or immigrate.
• Beak size is highly heritable.

• Rosemary and Peter Grant have been observing finches on Daphne Major for more than 40 years.
• They’ve noticed that finches with different beak shapes and sizes (heritable trait) prefer different kinds of seeds.
• After a drought, natural selection had caused the average beak size of the medium ground finches to increase, as their primary food source (smaller seeds) had vanished.
• 5 years later, after heavy rain, small seeds flourished again, giving a selective advantage to smaller beaks. Afterwards, beak size reduced again.
• Through this study, the Grants observed the heritability of beak size, the strength and direction of several episodes of natural selection, and the evolutionary response of the population.

Selection resulting from human activity. When breeders non randomly choose individuals with economically beneficial traits, they impose strong selection on those traits.

They show fluctuations in the direction and magnitude of selection.

• The movement or the migration of alleles from one population to another.
• Although many alleles that undergo gene flow are neutral, some may be deleterious or advantageous. Alleles that are advantageous in one population may be deleterious in another.
• Example: Being brightly colored for mimicry of coral snake in scarlet kingsnakes is beneficial in the south but increases predation in the north. Gene flow occurs between the two populations, but results in varying fitness.

Antipredator strategy used by prey to signal danger or a lack of palatability.

• No, not all types of selection lead to evolution.
• If heritability is low, populations won’t evolve even if they experience selection.

• Measure of the strength of phenotypic selection.
• Quantitative genetics: The difference in the mean of a trait in reproducing individuals and the mean of a trait for the general population.
• Directional selection occurs when the mean phenotype of breeding individuals differs from the mean of the individuals in the parent population.
• If the difference is large, selection is strong.

• The proportion of within-population variation in a trait that comes from genetic factors.
• (h2) is a number between 0 and 1 which represents how heritable a given trait is.
• The higher the heritability, the stronger the selection will be.
• If heritability is 0, evolution will not occur.

Favors individuals at one end of a trait distribution. Shifts to left or right.

Favors individuals with a trait near the population mean. Decreases variance (inceliyor mean’de)

Favors individuals at either end of the trait distribution. Here, if selection is strong enough, populations begin to diverge in phenotype and become dimorphic.

• Amount of variation there is in a phenotypic trait in the population.
• How much of the variation is heritable.

Evolutionary response ( R ) = h2 (heritability) x S (selection differential)

• Since more individuals are produced than can be supported by the available resources but population size remains stable, there must be fierce struggle for existence among the individuals of the population, resulting in the survival of only a very small part of the progeny of a generation.
• Survival in the struggle for existence is not random but depends in part on the hereditary constitution of surviving individuals. This unequal survival constitutes natural selection.
• Over the generations, this process of natural selection will lead to continuing, gradual change in the population.

• Natural selection will occur when:
• Individuals are variable in some traits.
• At least some of this variation is heritable.
• There is a struggle for survival or reproduction due to limited resources, and some individuals fare better than others.

• Morphological traits: Distinctive paper wasps fare better if they can recognize each other.
• Physiological traits
• Behavioral traits: Altruism, socialization, how well a bird can sing.

• Genetic differences.
• Environmental differences
• Interactions between genes and the environment.
• Measurement error.
• Ontogenetic (developmental stage) differences

Variation in phenotype across development; occurs mostly before maturation.

• Membrane enclosed nucleus
• Mitochondria (endosymbiosis of proteobacteria)
• Some have chloroplasts (endosymbiosis of cyanobacteria)
• Relatively large
• Generally multicellular such as protists
• Relatively complex

2 byA

• First step was the loss of the firm cell wall to form a flexible cell membrane.This allowed for larger cell size.
• To deal with increasing large cell size, infolding to increase surface area:volume ratio.
• Complex cell skeleton forms from microtubules and microfilaments.
• Internal membranes with ribosomes to synthesize proteins.
• The infolding cell membrane eventually enclosed the DNA, forming the nucleus
• Flagellum formed from microtubules, allowing the cell to propel itself.
• Endosymbiosis led to mitochondria and chloroplasts.

• They distribute daughter skeletons, allowing for mitosis to take place.
• In addition they allow for the development of flagellum.

• Primary endosymbiosis resulted from the incomplete phagocytosis of a bacterium.
• During endosymbiosis, rather than being ingested, the bacterium survived.
• When the host reproduced, subsequent generations would contain the descendants of the originally engulfed bacterium.
• The bacterial cells and the host cell developed a mutualistic symbiotic relationship: the host cell provided a safe environment and nutrients. The bacteria performed oxidative respiration, because it would’ve otherwise been poisoned by the increasing oxygen in the atmosphere at the time.

Aerobic proteobacterium.

Cyanobacterium.

• Synapomorphy of all plants.
• The common ancestor of glaucophytes, red algae, green algae, and land plants engulfed a cyanobacterium.
• All other occurrences of chloroplasts arose through secondary or tertiary endosymbiosis events.

A eukaryote, already carrying a symbiont, is engulfed by another eukaryote.

• Ancestor engulfed Green algae
• Euglenids (group of protists)

Common ancestor of stramenopiles and alveolates engulfed a red algae.

Dinoflagellates’ common ancestor engulfed a protist, which already had a chloroplast, because its ancestor had engulfed a red algae.

• Not a monophyletic group.
• Protists are eukarya that are not animals, plants or fungi.
• Have diverse characteristics.

• Unicellular
• Sacs called alveoli under the cell membrane to give it structure and support.
• Are photosynthetic and have chloroplasts that have been acquired through the secondary endosymbiosis of red algae.
• Dinoflagellates
• Ciliates
• plasmodium

• 2 flagella in an equatorial groove and longitudinal.
• Tertiary endosymbiosis of protist.
• A few are freshwater, many are abundant as marine plankton.
• Alveolites
• Endosymbionts of coral (corals are a result of quaternary endosymbiosis)
• Responsible for red tide blooms and bioluminescence (triggered by movement as an anti-predator defense mechanism).

Dinoflagellates release a neurotoxin in high temperatures, which leads the corals to expel them.

• paramecium,
• characterized by short, numerous flagella.
• Aquatic.
• Can be multinuclear.
• alveolites

• Intracellular parasites with vestigial chloroplasts.
• Alveolites.
• Complex of proteins at the apical prominence attach to and penetrate the host cell.

• Two flagella that are not of equal length. One the flagella is covered in tubular hairs.
• Many however, have lost their flagella.
• Brown algae
• diatoms

• Large multicellular algae
• Kelp forests, support a number of organisms such as sea otters, echinoderm sea urchins and sea lions.
• Stramenopiles
• Secondary endosymbiosis of red algae.

• Unicellular
• Stramenopiles
• Secondary lost their double flagella
• Secondary endosymbiosis of red algae.
• Deposit silica in their cell membranes and thus have beautiful shells.
• Major component of plankton and almost all are marine.
• 20% of carbon fixation on earth.

• Reduced or lost mitochondria
• Euglenids
• Giardia
• Trypanosoma

• Unicellular parasite
• Intestinal parasite
• Water borne
• Excavate
• Degenerate mitochondria and obtain energy from their host,

• Excavates
• Have mitochondria, one large flagellum
• Secondary endosymbiosis of green algae.
• Excavates

• Single celled, single enlarged mitochondria
• Some are free living while others are parasites
• Excavates
• Some cause debilitating sickness, such as sleeping sickness, Chagas’ disease, Leishmaniasis.

• Lobe shaped pseudopods (lobe shaped extension pods) used for movement
• Move by cytoplasmic streaming (slime molds)
• Amoeba
• Slime molds (unicellular, but multinucleate)

• Loss of the rigid cell wall and development of a flexible cell membrane.
• This led to larger size, the potential for infolding and compartmentalization, and endocytosis.

• Mitochondria is double membrane bound (its own membrane and the membrane that enclosed it.
• Mitochondria has its own DNA
• Mitochondria has its own circular chromosome. (like a proteobacterium)

• Chloroplast is double membrane bound.
• cpDNA is within chloroplast.

• The number of membranes around the chloroplast indicates the events of endosymbiosis.
• Glaucophytes, red algae, green algae and lands plants have a double membraned chloroplast.
• Dinoflagellates have 4 membraned chloroplasts.

• Has a chloroplast from primary endosymbiosis.
• Retain a small amount of peptidoglycan in chloroplast membrane.