BIOL 101 Exam 3 Study Guide

LECTURE 8 - EVOLUTION:

DARWIN’S VIEW OF LIFE:

- “Descent with modification” summarizes Darwin’s view of life

All organisms are related through descent from a common ancestor

Descendants spread into diverse habitats over millions of years and acquired  adaptations to their environments

The history of life resembles a tree with multiple branches from a common trunk

Species that are closely related share characteristics

ADAPTATIONS:

Excessive numbers of organisms lead to a struggle for survival

Adaptations: inherited characteristics of organisms that enhance their survival and reproduction in specific environments

The unequal ability of individuals to survive and reproduce leads to a gradual change in the characteristics of a population over generations

Natural selection is supported by evidence from artificial selection

FOSSILS:

- The study of fossils provides strong evidence for evolution

Fossils are the hard parts of organisms that remain after organic materials decay

The fossil record strongly supports the theory of evolution

Fossils appear in an ordered array within layers of sedimentary rocks

The fossil record reveals that organisms have evolved in a historical sequence

Many fossils link early extinct species with species living today

BIOGEOGRAPHY:

- The geographic distribution of species suggested to Darwin that organisms evolve from common ancestors

Isolated organisms resemble each other more than organisms in similar but distant places

COMPARATIVE ANATOMY, COMPARATIVE EMBRYOLOGY, HOMOLOGOUS STRUCTURES, AND VESTIGIAL STRUCTURES:

Comparative anatomy:

Homologous structures are features that often have different functions but are structurally similar because of common ancestry

Vestigial structures are remnants of structures that served important functions in an organisms ancestors

Comparative embryology:

Common embryonic structures in all vertebrates are evidence for common descent

POPULATION:

- Populations are the units of evolution:

Population:

A group of individuals of the same species living in the same place at the same time

May be isolated from other groups or concentrated

The smallest unit that can evolve

Population genetics:

Combines Darwin’s and Mendel’s ideas in studying how populations change genetically over time

The modern synthesis

Connects population genetics with other sciences

Focuses on population as the unit of evolution and central role of natural selection

EVOLUTION, MICROEVOLUTION, GENE POOL, SPECIES, GENE FLOW:

- Studying evolution at the population level:

Evolution: change in the prevalence of certain heritable characteristics in a population over a span of generations

Gene pool: the total collection of genes in a population at any one time

Microevolution: a change in the relative frequencies of alleles in a gene pool

Species: a group of populations capable of interbreeding and producing fertile offspring

The gene pool of a non-evolving population remains constant over the generations

In a non-evolving population, the shuffling of alleles that accompanies sexual reproduction does not alter the genetic makeup of the population

In Hardy-Weinberg equilibrium, the frequency of each allele in the gene pool will remain constant unless acted upon by other agents

Genetic drift: change in the gene pool of a population due to chance

Can alter allele frequencies in a population

The smaller the population, the greater the impact

BOTTLENECK EFFECT AND FOUNDER EFFECT:

Bottleneck effect: an event that drastically reduces population size

Founder effect: colonization of a new location by a small number of individuals

THREE WAYS THAT NATURAL SELECTION CAN ALTER VARIATION IN A POPULATION:

- Natural selection:

Best-adapted individuals have the most reproductive success

Results in accumulation of traits that adapt a population to it’s environment.

Natural selection can alter variation in a population in three ways:

Stabilizing selection: favors intermediate phenotypes

Directional selection: acts against individuals at one of the phenotypic extremes

Disruptive selection: favors individuals at both extremes of the phenotypic range

SEXUAL DIMORPHISM AND SEXUAL SELECTION:

Sexual selection may produce sexual dimorphism:

Sexual dimorphism:

The distinction in appearance between males and females of a species

Sexual selection:

The determining of “who mates with whom”

Leads to the evolution of secondary sexual characteristics that may give individuals an advantage in mating

LECTURE 9 - PROKARYOTES:

THE FIRST CELLS - PROKARYOTES:

- Earth formed 4.6 billion years ago

The oldest fossil organisms are prokaryotes  dating back to 3.5 billion years ago

Prokaryotes are single celled organisms in the domains Bacteria and Archaea.

Prokaryotes are the most abundant organisms on Earth

They thrive in most environments, including places to acidic, salty, cold, or hot for most other organisms

Some prokaryotes colonize the bodies of other organisms

PROTOCELLS:

Replication and metabolism are key properties of life and may have appeared together in early protocells

Protocells may have been fluid-filled vesicles with a membrane like structure

In water, lipids and other organic molecules can spontaneously form vesicles with a lipid bilayer

Vesicles exhibit simple reproduction and metabolism and maintain an internal chemical environment.

CYANOBACTERIA:

Cyanobacteria are gram-negative photoautotrophs that generate O2 through plantlike photosynthesis

Plant chloroplasts likely evolved from cyanobacteria by the process of endosymbiosis

Cyanobacteria are common members of the phytoplankton in marine and freshwater communities

CELL STRUCTURES AND FEATURES: PEPTIDOGLYCAN, CAPSULE, ENDOSPORES, PILI, TAXIS:

Bacterial cell walls contain peptidoglycan, a network of modified sugars cross linked by polypeptides

Archaeal cell walls contain polysaccharides and proteins but lack peptidoglycan.

A polysaccharide or protein layer called a capsule covers many prokaryotes and allows them to adhere to the substrate or each other

Some bacteria develop resistant cells called endospores when they lack water or essential nutrients

Pili (or sex pili) are longer that fimbriae and allow prokaryotes to exchange DNA

In a heterogeneous environment, many bacteria exhibit taxis, the ability tome toward or away from a stimulus

GRAM POSITIVE V.S GRAM NEGATIVE BACTERIA:

Scientists use the gram stain to classify bacteria by cell wall composition

Gram-positive bacteria have simpler walls with a large amount of peptidoglycan

Gram-negative bacteria have less peptidoglycan and an outer membrane that can be toxic

Many antibiotics target peptidoglycan and damage bacterial cells walls

Gram-negative bacteria are more likely to be antibiotic resistant

Gram-Positive bacteria include:

Streptomyces, which are a source of antibiotics

Bacillus anthracis, the cause of anthrax

Clostridium botulinum, the cause of botulinum

Staphylococcus and Streptococcus, which can be pathogenic

NUTRITIONAL MODES: PHOTOTROPHS, CHEMOTROPHS, AUTOTROPHS, HETEROTROPHS:

- Prokaryotes can be categorized by how they obtain energy and carbon

Phototrophs obtain energy from light

Chemotrophs obtain energy from chemicals

Autotrophs require C02 as a carbon source

Heterotrophs obtain carbon from organic nutrients

OXYGEN REQUIREMENT: OBLIGATE AEROBES, OBLIGATE ANAEROBES, FACULTATIVE ANAEROBES:

- THE ROLE OF OXYGEN IN METABOLISM:

Prokaryotic metabolism varies with respect to O2

Obligate aerobes require O2 for cellular respiration

Obligate anaerobes are poisoned by O2 and use fermentation or anaerobic respiration

Facultative anaerobes use O2 if it is available, but can survive without it

TRANSFORMATION, TRANSDUCTION, CONJUGATION:

Some prokaryotic cells can take up and incorporate foreign DNA from the surrounding environment in a process called transformation

Transduction is the movement of genes between prokaryotic cells by phages (viruses that infect bacteria)

Conjugation is a process by which genetic material is transferred directly between prokaryotic cells

CHLAMYDIAS, SPIROCHETES, CYANOBACTERIA:

Chlamydias are disease causing parasites that can only live within animal host cells

For example, Chlamydia trachoma’s causes blindness and the sexually transmitted disease nongonococcal urethritis

Spirochetes are helical gram-negative heterotrophs

Many species are free-living, but some parasitic

For example. Treponema palladium causes syphilis and Borrelia burgdorferi causes Lyme disease

Cyanobacteria are gram-negative photoautotrophs that generate O2 through plantlike photosynthesis

Plant chloroplasts likely evolved from cyanobacteria by the process of endosymbiosis

Cyanobacteria are common members of the phytoplankton in marine and freshwater communities

ARCHAEA:

Archaea share some traits in common with bacteria and others with eukaryotes

Some archaea live in extreme environments and are called extremophiles

Extreme halophiles either tolerate or require a highly saline environment

Extreme thermophiles thrive in a very hot environments

- Many archaea live in more moderate environments

MUTALISM, COMMENSALISM, PARASITISM:

These symbiotic relationships increase the fitness of one or both organisms

In mutualism, both organisms benefit

In commensalism, one organism benefits while neither harming nor helping the other in any significant way

In parasitism, an organism called a parasite harms but does not kill its host

EXOTOXINS AND ENDOTOXINS:

Pathogenic prokaryotes typically cause disease by releasing exotoxins or endotoxins

Exotoxins are secreted and cause disease even if the prokaryotes that produce them are not present

Endotoxins are released only when bacteria die and their cell walls break down

LECTURE 10 - EUKARYOTES:

BASIC FEATURES OF THE FOLLOWING ORGANISMS: PROTISTS, DIPLOMONADS, PARABASALIDS, EUGLENOZOANS, DIATOMS, ALVEOLATES, DINOFLAGELLATES, AMOEBA, FORAMS:

Protist is the informal name of the diverse group of mostly unicellular eukaryotes

Some protists, like the ciliate Didinium, are able to perform dramatic shape changes due to the structural complexity of their cells.

- These two groups plastids and have reduced mitochondria; most live in anaerobic environments

Diplomonads:

Have reduced mitochondria called mitosomes

Derive energy from anaerobic biochemical pathways

Are often parasites, for example, Giardia intestinalis

Move using multiple flagella

Parabasalids:

Have reduced mitochondria called hydrogenosomes that generate some energy anaerobically

Include Trichomonas vaginalis, a sexually transmitted parasite

Euglenozoa is a diverse clade that includes predatory heterotrophs, photosynthetic autotrophs and parasites

Their main distinguishing feature is a road with a spiral or crystalline structure aside their flagella

This clade includes the euglenoids and kinetoplastids

Diatoms are highly diverse, unicellular algae with a unique two art glass like wall of silicon dioxide

The alveolate have membrane enclosed sacs (alveoli) just under the plasma membrane

Dinoflagellates and ciliates are members of the alveolar clade

Dinoflagellates have two flagella, and each cell is reinforced by cellulose plates

Amoebas move and feed by pseudopodia, extensions that bulge from the cell surface

Most rhizarian amoebas have threadlike pseudopodia

Pseudopodia extend through the pores in the test and are used for swimming, feeding and test formation

Forams and cercozoans are members of the rhizarian clade

Forams, are named for their porous shells, called tests

Many forams also receive nourishment from symbiotic algae

Forams include both marine and freshwater species

ENDOSYMBIOSIS:

 Endosymbiosis, a symbiotic relationship in which one organism lives inside the body or cell of another organism.

 Endosymbiont theory proposes that mitochondria and plastids were formerly small prokaryotes that began living within larger cells

An endosymbiont is a cell that lives within a host cell

The relationship between endosymbiont and host cells could have become mutually beneficial.

Over time, the host and endosymbionts would have become a single organism

Key evidence supporting an endosymbiotic origin of mitochondria and plastids:

Inner membranes are similar to plasma membranes of prokaryotes

Division is similar in these organelles and some prokaryotes

DNA Structure is similar to that of prokaryotes

Their ribosomes are more similar to prokaryotic than eukaryotic ribosomes

Secondary endosymbiosis occurred when eukaryotic algal cells were ingested by heterotrophic eukaryotes

RED AND GREEN ALGAE:

- RED ALGAE:

Red algae are reddish in color due to an accessory pigment called phycoerythrin

The color varies from greenish-red in shallow water to dark red or almost black in deep water

Red algae are usually multicellular; the largest are seaweeds

They reproduce sexually, forming unflagellated gametes, which depend on water currents to unite for fertilization

GREEN ALGAE:

Green algae have many molecular and cellular similarities with land plants

For example, their chloroplasts have similar structure and pigment composition to those of land plants

Green algae are divided into charophytes and chlorophytes

Charophytes are most closely related to land plants

Most chlorophytes live in fresh water, although many are marine and some are terrestrial

Nearly all species of chlorophytes reproduce sexually.

RADIAL V.S BILATERAL SYMMETRY:

Animals can be categorized according to the symmetry of their bodies or lack of it

Some animals have radial symmetry which is symmetry around a central axis

Others have bilateral symmetry which is divided into two symmetrical halves

Many radial animals are sessile while bilateral animals often move actively; their central nervous system enables coordinated movement.

ECTODERM, ENDODERM, MESODERM:

Ectoderm, the outer germ layer, gives rise to the outer covering and the central nervous system

Endoderm, the innermost germ layer, gives rise to the digestive tract and organs including the liver and lungs in vertebrates

Mesoderm fills the space between the ectoderm and the endoderm and gives rise to muscles and organs

CHORDATES, AMPHIBIANS, AMNIOTES, REPTILES, BIRDS AND MAMMALS:

Chordates are bilateral animals that belong to the animal clade Deuterostomia

All chordates share four derived characters

Four key characters of chordates:

Notochord, a flexible rod providing support

Dorsal, a hollow nerve cord, which develops into the brain and spinal cord

Pharyngeal slits or pharyngeal clefts, which function in suspension feeding, as gills, or as parts of the head

Muscular, post-anal tail

AMPHIBIANS:

Amphibians are represented by about 6,150 species including salamanders, frogs, and caecilians

Many amphibians have gill breathing aquatic larvae that undergo metamorphosis into lung breathing adults that live on land

Their skin must also be kept moist to facilitate gas exchange

AMNIOTES:

Amniotes colonized a more extensive range of dry habitats than did amphibians

Amniotes are a group of tetrapods whose living members are the reptiles (including birds) and mammals

Amniotes are named for the major derived character of the clade, the amniotic egg, which contains four membranes that protect the embryo

Reptiles share several derived characters

They have scales that create a water proof barrier

Most have internal fertilization and lay shelled eggs on land

Most are ectothermic, absorbing external heat to regulate body temperature; birds are endothermic, maintaining body temperature through metabolism.

Birds are a diverse group of flying reptiles that evolved about 160 million years ago

Birds have weight saving adaptations for flight:

They lack a urinary bladder

Females of most species have one ovary

They lack teeth

Other adaptations for flight include

Wings and feathers

Large pectoral (breast) muscles

Efficient respiratory and circulatory systems including a four chambered heart

Color vision and acute eyesight

Well developed visual and motor areas of the brain

MAMMALS:

Mammals, the other extant lineage of amniotes have many derived traits

Mammary glands that produce milk

Hair

A fat layer under the skin

The kidney, which conserves water during waste removal

A high metabolic rate, due to endothermy

A relatively large brain

Differentiated teeth