Biology Exam Review PDF

Biology Exam Review Ian Hobdari Diversity Of Living Things - Lessons 1-4 Genetics - Lessons 1-8 Evolution - Lessons 1-6 Animal Systems - Lessons 1-4 Diversity of Living Things Lesson #1 Key Concepts: -​ Biodiversity is the variety of life...

Biology Exam Review Ian Hobdari Diversity Of Living Things - Lessons 1-4 Genetics - Lessons 1-8 Evolution - Lessons 1-6 Animal Systems - Lessons 1-4 Diversity of Living Things Lesson #1 Key Concepts: -​ Biodiversity is the variety of life on Earth Characteristics of all Living Things: -​ Made of cells -​ Respond to their environment -​ Reproduce -​ Adapt to their surroundings -​ Grow and develop -​ Use and need energy​ - A good way to remember this is by using the term “MR RAGU” Classifying Species: -​ Biological species is a group of organisms -​ For example, the labradoodle is not infertile (meaning they can produce) and so the labrador and poodle are part of the same species -​ A zorse (zebra + horse hybrid) are fertile, but their offspring are not, meaning they are not part of the same species -​ A hybrid is offspring that is successfully produced from two animals -​ Taxonomy: the branch of biology that classifies organisms and assigns each organism a universally accepted name 3 Levels of Biodiversity: Genetic Biodiversity Species Diversity Ecological Diversity It is important because it benefits It is important because organisms The variation in the different a species survivor rely on other species for an ecosystems, it is important to hold increased rate of survival, and different species in their different their survival relies on eachother habitats Threats to Biodiversity: 1)​ Habitat Loss 2)​ Invasive Species 3)​ Population 4)​ Pollution 5)​ Over Exploitation Darwin’s Theory of Evolution 1)​ Organisms produce more offspring than can survive, from the offspring that do survive, many will never reproduce 2)​ Because more organisms are produced than can survive, there is intense competition for resources 3)​ Individuals that are best suited to their environment survive and reproduce, while organisms that are less suited for their environment often die or will not reproduce 4)​ The species that are alive on Earth today are descended with modification 5)​ These all make up the process of “natural” selection that causes many of the species to change over time Early Attempts at Classification (Aristotle): Organisms were first classified over 2000 years ago by the greek philosopher, Aristotle 1)​ Aristotle first sorted organisms into two groups: Plants and Animals 2)​ He divided the animals into three groups:​ a) Land Dweller​ b) Air Dweller​ c) Water Dweller 3)​ He also divided the plants into three groups based off of their stems​ a) Trees​ b) Herbs​ c) Shrubs There were many problems with this system of classification 1)​ Many organisms were being placed into groups in which they had no real relationship with each other 2)​ The use of common names was very confusing, for example catfish, jellyfish and starfish 3)​ Many new organisms were being discovered and needed to be classified The Linnaeus System of Classification: 1)​ Philosopher Carolus Linnaeus set up a classification system based on structural similarity, he thought that organisms that looked alike were the most closely related 2)​ Linnaeus developed a system that placed an organism in a particular group and assigned it a particular name 3)​ He developed a naming system called binomial nomenclature, which is the system of assigning an organism a scientific name 4)​ He first divided all organisms into large groups that he called kingdoms. He based his classification on two kingdoms: The plant and animal kingdom -​ More recently, scientists have developed a broader group; Domain -​ The three types of domain are​ a) Eukarya​ b) Bacteria​ c) Archaea  -​ Bacteria and archaea are both single-cellular organisms, while eukarya contains all organisms with complex, multicellular structures 5)​ The 8 levels of classification: ​ Kingdom → Phylum → Class → Order → Family → Genus → Species -​ A good way to remember this is by saying: Did King Phillip Come Over For Good Spaghetti -​ A species contains only one kind of organism Rules of Binomial Nomenclature: -​ The scientific name are in latin always consists of two words: The genus and the species -​ The first name is always capitalized, while the second name is not, and the two names are always the genus followed by the species Lesson #2 Modern Taxonomy: -​ Phylogeny is the evolutionary history of an organism -​ To show the evolutionary relationship between different groups of organisms, scientists construct a phylogenetic tree -​ A phylogenetic tree is a family tree that shows the evolutionary relationships thought to exist among different groups of organisms Modern Taxonomy: -​ Modern taxonomy is based on the morphology of different species (structure) -​ This was the basis for Linnaeus’ system of classification Homologous Structures Analogous Structures Vestigial Structures Structures in different species that Structures in different species that A structure that is reduced in size are similar because of common are similar in function but not in and seems to be “left over” from a ancestry. structure and are not derived from previous ancestor. For example, the bones found in a common ancestor. For example, the human appendix the wing of a bird, the wing of a For example, the wing of a bird or wisdom teeth. bat, and the forearm of a human. and the wing of a butterfly. -​ The greater number of homologous structures two organisms share, the more closely related they are thought to be -​ Similarity in cell structure provides evidence that organisms may be related -​ Scientists now group organisms into categories that represent lines of evolutionary descent or phylogeny -​ Fossils show that organisms alive today are similar to organisms that are now extinct, for example 25 breeds of dogs all came from a wolf-like ancestor -​ Three easy ways we can tell organisms apart are: Biochemical Similarities Genetic Similarities Embryological Similarities Similarities of chemical Do the two organisms have the Similarities in embryological compounds found within cells can same number or type of development provide evidence of be used as evidence to show chromosomes? phylogenetic relationships relationships between organisms Two organisms that bear no Some organisms show no resemblance to one another similarities as adults, but are very A comparison between the anatomically may still be related similar as embryos. An example of proteins of two organisms occurs to one another. Two organisms this is an amnion which is a as a “molecular clock”. Simple that look nothing alike may still fluid-filled sac that surrounds the mutations occur all the time, have similar genes in their DNA embryos of some vertebrates. The causing slight differences in the This genetic similarity is an embryos of fish and amphibians indication that yeast and humans lack amnion. The embryos of DNA and the proteins being built. share a common ancestor reptiles, birds and mammals When the proteins of two possess an amnion. On the basis different organisms are The more similar DNA sequences of this shaped embryological compared, the number of are within two species, the more structure, reptiles, birds and differences in amino acid recently they shared a common mammals are grouped together sequences is a clue to how long ancestor, the more two species and are referred to as amniotes. have diverged, the less similar their DNA will be  ago two species diverged from a shared common ancestor Cladistics: -​ Cladistics is a relatively new method of classifying organisms -​ Cladistics identifies the characteristics of organisms that are “evolutionary innovations” these innovations are new characteristics that arise among organisms over time -​ Cladistics uses a feature called shared characters and derived characters Shared Characters Derived Characters A feature that all members of the group have in A feature that evolved only within the group under common, for example feathers in birds or hair in consideration, for example feather in birds (since mammals birds are the only animals with feathers, it is assumed feathers evolved within the bird group and were not inherited by an ancestor -​ Shared derived characters are strong evidence of common ancestry between the organisms that share them. Organisms that share one or more derived character most likely have a common ancestor -​ Clades is used to describe a group of organisms that include a ancestor plus all off its descendants, the relationship between the organisms in a clade can be represented by a cladogram (shown below) -​ A cladogram is a diagram that shows the evolutionary relationships among a group of organisms -​ This cladogram shows the relationship between 5 different organisms alive on earth today -​ A cladogram includes an organism that is only distantly related, knows as the “out-group”, in this cladogram the out-group is the Lamprey -​ The other organisms are known as the “in-group” and have one or more of shared derived character -​ The in group of this cladogram is Sea Bass, Antelope, Bald Eagle and  the alligator, which all possess one or more shared derived characters from the lamprey Lesson #3 Kingdoms and Domains -​ A kingdom called the “monera kingdom” was formed in the 1950’s and included bacteria and blue-green algae. These are the simplest of all living organisms. -​ There are currently six known kingdoms, and three domains. The six kingdoms fall into 1 of 3 domains: Kingdom Kingdom Kingdom Kingdom Kingdom Kingdom Archaebacteria Eubacteria Protists Plantae Fungi Animalia Domain Archaea Domain Bacteria Domain Eukarya -​ A kingdom comparison would look something like this:  All Living Things Domain Bacteria Archaea Eukarya Kingdom Eubacteria Archaebacteria Protista Fungi Plantae Animalia Cell Type Prokaryotic Prokaryotic Eukaryotic Eukaryotic Eukaryotic Eukaryotic Cell Thick and rigid Cell walls do Contains Cell walls Cell walls No cell walls Structure cell walls not contain organisms that composed of composed of and no composed of peptidoglycans are neither chitin and cellulose, chloroplasts Peptidoglycans Cell animal, plant have no chloroplasts membranes or fungi chloroplasts are present contain Cell walls unusual lipids composed of not found in cellulose in any other some organisms organisms and “Ancient have organisms” chloroplast and very primitive Cell Unicellular Unicellular Most are Most are Multicellular Multicellular Organization Unicellular Unicellular Food Autotrophs + Includes Autotrophs + heterotrophs Autotrophs heterotrophs Getting heterotrophs Autotrophs + heterotrophs heterotrophs Examples of E-coli, strep Methanogen Amoeba, Mushrooms, Mosses, Mammals, organisms (has no thermophiles algae, slime yeats molds, ferns, fish, birds, nucleus) (has no and mold mildews and flowering reptiles, nucleus) smut plants amphibians -​ Autotroph: An organism that makes it own food (plants through photosynthesis) -​ Heterotroph: An organism that gets its food from other organisms -​ Prokaryotic: A unicellular organism that doesn’t have a nucleus -​ Eukaryotic: A multicellular organism that has a nucleus Factors That Keep Organisms Apart: -​ Physical characteristics: Mating is impossible under natural conditions for most organisms -​ Mating occurs, but the offspring do not survive: bullfrog eggs may be fertilized by the sperm of a leopard frog, the eggs develop to a point but do not survive -​ The offspring may survive, but they are not fertile: Horse + Donkey = Mule -​ Geographical barriers: many organisms simply do not come into contact with one another  -​ Behavioural barriers: Many organisms, especially in the animal kingdom, will not mate unless certain behaviours are exhibited Necessities for Organisms: Nutrition Take in material (i.e.) food for growth Respiration Releases energy from food for cellular process Movement Move using energy consumed by the organism Excretion Release waste products from cellular processes Growth Living organisms use food to grow in size or number of cells Reproduction Produce offspring Sensitivity Sense and respond to stimuli in the environment What is a Virus? -​ Viruses are microscopic particles capable of only reproducing within existing living cells (host cells) -​ Viruses are classified as non-living particles because they cannot perform any of the processes that are the required characteristics of life -​ Viruses do share one characteristic with organisms: they contain genetic material (DNA) that can be passed, however they require a host cell to reproduce Basic Structure of a Virus -​ All viruses contain nucleic acid (DNA or RNA) in core, surrounded by capsid (protein coat) and an outer envelope -​ Viruses are less than 0.1 micrometres in diameter (1 micrometer = (10 to the negative 6m))  -​ Bacteriophages (complex viruses) are viruses that invade and destroy bacteria cells, they have unique shapes and distinct head and tail regions -​ They are the most abundant biological agent on Earth Viral Replication and Transmission -​ There are two different types of ways viruses can replicate within a host cell: Lytic Cycle Lysogenic Cycle In the lytic cycle, the virus hijacks the host cell using In the lysogenic cycle, the virus incorporates its it to reproduce the virus. The host cell is destroyed in genetic material into the host cell’s genome, infecting the process. it from within. The host cell remains intact There are 4 steps to the Lytic Cycle:​ 1) Attachment to host cell In the lysogenic Cycle, the host cell is not destroyed 2) Synthesis of new virus Viral DNA can remain in a dormant state (lysogeny) 3) Assembly of new virus for years, the host continues to divide with viral DNA 4) Release of virus, destroying the cell inserted into its own DNA The lytic cycle can take as few as 25-45 minutes to When triggered by changes, viral DNA becomes produce as many as 300 new viruses. Some examples active, and the virus enters the lytic cycle. Examples are common cold, ebola and SARS include herpes and HPV Genetics Lesson #1 The Basics: -​ Genetics is the study of genes, heredity, and genetic variation in living organisms. -​ A trait is a characteristic of an organism. It can be inherited or can be shaped by the environment -​ Heredity is the passing of information from one generation to the next -​ This genetic information is passed on by deoxyribonucleic acid, DNA, a molecule stored in pieces as chromosomes in the nucleus of every cell -​ DNA is a molecule stored in pieces as chromosomes in the nucleus of every cell  -​ DNA is organized into genes, units of inherited information that carry a code for a specific protein DNA -​ Proteins are assembled piece by piece to exact specifications -​ This information detailing the specific structure of the proteins inside our bodies, is stored in a set of molecules called nucleic acids -​ DNA is a nucleic acid, and exists as a mass of very long fibres called chromatin. -​ Chromatin condenses into a chromosome, a package of DNA that is 3 meters long when stretched out, wrapped around proteins called histones. -​ Human cells contain 46 chromosomes, 23 from the egg and 23 from the sperm. A complete set of chromosomes is shown in a karyotype. -​ A carp has 104 chromosomes. An onion has 6. They are always an even number, because they represent a set. -​ The traits of an organism are determined by the order of 4 different molecules called nitrogenous bases (A, T, C, G).​ The Structure of DNA: -​ The subunit or building block of DNA is the nucleotide, which is made of 3 components: a)​ Sugar b)​ Phosphate group c)​ Nitrogenous base -​ The nucleic acids are very large molecules that have two main parts. A. The backbone of a nucleic acid is made of alternating sugar and phosphate molecules bonded together in a long chain. B. Each of the sugar groups in the backbone is attached to a third type of molecule called the nitrogenous base. -​ DNA gets its name from the sugar molecule contained in its backbone (deoxyribose) Four different nucleotides occur in DNA: 1.​ adenine (A) 2.​ cytosine (C) 3.​ guanine (G) 4.​ thymine (T). -​ The nucleotide bases of the DNA molecule form complementary pairs: -​ Complementary pairing occurs due to hydrogen bonds: Adenine always forms 2 hydrogen bonds with thymine Cytosine always forms 3 hydrogen bonds with guanine -​ Finally, this double-stranded system is found in a helical shape called the double helix. -​ The letters (bases) form words (codons) that in turn create sentences (genes) that code for different amino acids. Proteins are chains of amino acids that perform a specialized function. The human genome contains over 25,000 genes. Chromosomes: -​ Both prokaryotes and eukaryotes carry their DNA in a structure called a chromosome. -​ However, there are differences in prokaryotic and eukaryotic chromosomes (also recall that prokaryotic cells have smaller circular pieces of additional DNA called plasmids.) -​ A chromosome consists of DNA & packaging proteins to keep it organized. -​ Most of the time, it’s in the structural form called chromatin (long unwound strands). -​ In eukaryotic cells, chromosomes take the commonly recognized X-shape during cell division. Genes, Loci, and the Genetic Sequence: -​ The order of the nitrogenous bases is a code, or a language. -​ The code is read in sections called genes, by equipment in the cell. -​ Each gene codes for a protein (i.e. traits of the organism) -​ The location of a gene in the chromosome is called the locus (plural: loci). -​ The equipment of the cell reads genes and translates it into specific proteins. -​ The proteins are responsible for traits in the organism (e.g. eye colour, height, location of the limbs, hormones, heart tissue, etc.) The Human Genome: -​ The human genome consists of 3 billion base pairs. -​ It’s actually 6 billion base pairs, because you have two copies of each chromosome. -​ There are approximately 25,000 genes that code for proteins. Lesson #2 The Cell Cycle: -​ The cell cycle is a series of events that are ongoing and serve two main purposes: ​ 1. to create daughter cells  2. to allow growth and maturation of these daughter cells until cell division occurs again. - Each of the different stages of the cell cycle is designated by a particular letter that stands for what happens in that phase. - S phase— ”S” for Synthesis of DNA - G1 and G2 phase–- ”G” for Gap - M phase – “M” for mitosis - G1 phase—primary growth and maturation of new cells immediately following division; - S phase --point during which the DNA is replicated in anticipation of a division event. Hereditary material (DNA) makes an exact copy of itself so that upon cell division, each duplicate will move to each new cell, thus creating identical daughter cells. This, of course, is the overall purpose of cell division. -​ G2 phase— secondary growth and maturation following DNA replication; M phase—stage in which mitosis and cytokinesis occurs to create two new daughter cells from a single parent cell. -​ Mitotic events occupy only a small fraction of the cell cycle. Much of the cell’s “time” is spent in the G1, S and G2 phases. The G1, S and G2 phases are combined under the singular heading of interphase, which takes up 90% of the life cycle of the cell, leaving only 10% of the cycle engaged in actual mitotic events. Apoptosis: - All somatic cells have the same life cycle of growth and maturation, DNA replication and division. At some point in a cell’s “life”, the cell is programmed to slow and finally cease division. -​ Programmed cell death is called apoptosis. -​ Cancer cells continue to divide incessantly, forming a mass called a tumor. Function of Mitosis: Mitosis ensures genetic continuity by facilitating the division of replicated DNA material and separation into two identical daughter cells. Each daughter cell is capable of the exact same function(s) as that of the parent cell. In this manner, cells can be replaced without losing the overall function of the particular tissue in question. Cell division, in turn, allows for tissue repair and maintenance to occur without disrupting the proper functioning of the organ. Phases of Mitosis: Chromosomes become visible, the nucleolus disappears, the mitotic spindle Prophase forms, and the nuclear envelope disappears. The chromosomes become arranged on the metaphase plate and are Metaphase attached to the now fully formed spindle. Sister chromatids separate, and the now-daughter chromosomes move to Anaphase opposite poles of the cell. Telophase Chromosome sets assemble at opposite poles, a nuclear envelope reforms around each set, and cytokinesis (division of the cytoplasm) usually follows. -​ Cytokinesis is the process in which the cytoplasm is divided in two. A cleavage furrow forms and the cell membrane pinches off the cytoplasm into two halves to form two cells. -​ All of the genetic material in the cell must be copied prior to cell division. -​ An exact copy of each cell’s DNA is made via DNA replication. -​ Two identical copies of the same chromosome, known as sister chromatid, are joined tightly together at the centromere. Chromosome VS. Chromatid: -​ Remember: The number of chromosomes = the number of centromeres -​ As DNA replicates a small amount of DNA is lost at its ends. -​ To ensure that no important information is lost, telomeres form protective caps of non-essential DNA  sequences at the ends of the chromosome. Mutations: -​ A mutation is a change in the genetic material—the DNA. Mutations are important because they may have negative or positive effects on the organism and/or its offspring. -​ Finally, mutations are a major source of genetic variation among species and individuals. They lead to changes in the structure of the DNA, which may have some evolutionary consequence. -​ There are a variety of different types of mutations that occur because of errors in DNA replication and the division of chromosomes. -​ Induced mutations occur as a result of the interaction of DNA with some outside factor—a mutagen. -​ A mutagen is a natural or man-made chemical that has the potential to alter the structure and/or sequencing of the DNA molecule. -​ Most mutagens are harmful. For example, poisonous mustard gas used in both world wars caused mutations in nerve cells that led to interference with the proper functioning of these cells. Other chemical mutagens have been found in the composition of cigarettes and linked to the transformation of lung cells—lung cancer Lesson #3 Types of Cell Reproduction: -​ Asexual reproduction involves a single cell dividing to make 2 new, identical daughter cells. Mitosis, fragmentation & binary fission are examples of asexual reproduction -​ Sexual reproduction involves two cells (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells. Meiosis is an example of sexual reproduction. Meiosis: -​ Meiosis is a form of cell division that results in 4 cells which each contain half of the number of chromosomes as the original parent cell. -​ It’s required for sexual reproduction to occur (i.e. the combining of genetic material). In many animals, like humans, meiosis occurs in the sex organs (ovaries and testes). -​ Karyotype = the collection of all an individual’s chromosomes, which is typically a total of 46. Some people have fewer than or more than 46 chromosomes, which results in a variety of outcomes. -​ Recall that chromosomes are organized into pairs called homologous pairs. -​ They are paired based on their size, shape, and function. Offspring receive one of each pair from each biological parent. -​ While the information on each homologous chromosome is very similar, they aren’t identical to each other. -​ They contain the same genes, but the information in those genes sometimes differ slightly (i.e. traits inherited from each parent are different). -​ An allele is a variation of a gene. Why do we need Meiosis? -​ It is the fundamental basis of sexual reproduction. It produces egg and sperm cells (gametes) Two haploid (1n) gametes are brought together through fertilization to form a diploid (2n) zygote.  -​ Before beginning meiosis, the cell must complete interphase (just like before mitosis). -​ The cell grows during G1 phase, replicates its genetic material during S phase, and grows and prepares for cell division in G2 -​ Now the cell has 46 chromosomes, and 92 chromatids (double the number of chromatids the cell had in G1) -​ Replication is the process of duplicating a chromosome -​ Occurs prior to division -​ Replicated copies are called sister chromatids -​ Held together at centromere -​ Meiosis must reduce the chromosome number by half. Fertilization then restores the 2n number Meiosis Overview: -​ Occurs as two stages of cellular replication -​ Begins with one cell, then two, and finishes with 4 cells -​ The first cell which will undergo meiosis is called the parent cell (diploid). The cells that are produced from meiosis are called gametes (haploid)  Meiosis 1: Prophase 1: -​ Chromosomes condense and the nuclear envelope breaks down -​ In mitosis, the chromosomes begin to arrange in one single file line down the middle of the cell. In meiosis, a pair of homologous chromosomes undergo synapsis, i.e. they line up beside each other -​ This forms a tetrad (i.e. 4 chromatid aligned) Crossing Over: -​ Crossover occurs during synapsis (Prophase I), when sections of DNA are exchanged between the homologous pairs. -​ These events are random, producing more genetic diversity in a species. Up to 25 crossovers can happen for each homologous pair during synapsis Meiosis 1: Metaphase 1: -​ The tetrads align in the midline of the cell. As in mitosis, this midline is called the metaphase plate. The centromeres are oriented toward the opposite cell poles -​ Homologous pairs of chromosomes align along the equator of the cell Meiosis 1: Anaphase 1: -​ Chromosomes move to the opposite cell poles. Spindle fibers pull the chromosomes to each pole. -​ Unlike in mitosis, sister chromatids remain together and the homologous pairs are separated Meiosis 1: Telophase 1 and Cytokinesis: -​ Homologous chromosomes continue moving toward the poles. Each pole becomes a haploid (i.e. 23 chromosomes, 46 chromatid) -​ Cytokinesis also occurs as meiosis 1 finishes. The genetic material does not replicate again Meiosis 2: Prophase 2: -​ The starting cells are haploid cells made in meiosis 1. This means that they don’t have homologous pairs of chromosomes, they only have one copy of each. -​ There is no interphase between meiosis 1 and meiosis 2, therefore chromosomes are not replicated prior to prophase 2. -​ The chromosomes begin migrating to the middle line. Meiosis 2: Metaphase 2: -​ The chromosomes line up in a single file at the cell’s center, forming the metaphase plate. Meiosis 2: Anaphase 2: -​ Sister chromatids of each chromosome separate and begin moving in opposite poles. -​ Sister chromatids separate from one another. They are now known as daughter chromosomes. -​ The two cell poles also move further apart. Each pole contains a complete set of chromosomes. Meiosis 2: Telophase 2 and Cytokinesis:  -​ A nucleus begins to form in each pole. -​ Cytokinesis is also occurring. -​ Four daughter cells have been produced. All of the daughter cells have half the number of chromosomes the original parent cell had. Results of Meiosis: -​ Gametes (egg & sperm) form Four haploid cells with one copy of each chromosome -​ One allele of each gene -​ Different combinations of alleles for different genes along the chromosome Meiosis Summary: -​ Preceded by interphase which includes chromosome replication. -​ Two meiotic divisions --- Meiosis I and Meiosis II. -​ Called Reduction- division Original cell is diploid (2n) -​ Four daughter cells produced that are monoploid/haploid (1n) -​ Daughter cells contain half the number of chromosomes as the original cell, it produces gametes (eggs & sperm) -​ Occurs in the testes in males (Spermatogenesis) and occurs in the ovaries in females (Oogenesis) -​ Start with 46 double stranded chromosomes (2n) -​ After 1 division - 23 double stranded chromosomes (n), after 2nd division - 23 single stranded chromosomes (n) -​ Occurs in our germ cells that produce gametes Lesson #4 Gametogenesis: -​ Formation of gametes (through the process of meiosis) ​ a) Male --> spermatogenesis ​ b) Female --> oogenesis -​ increases genetic diversity within population  -​ Diversity is generated through… ​ a) Crossing-over (makes diverse chromosomes). ​ b) Independent assortment of chromosomes (each gamete gets a different combo of chromosomes from the biological grandparents). ​ c) Random fertilization (random sperm meets with random mature egg).​ Spermatogenesis: -​ One parent diploid cell (46 chromosomes) produces four haploid sperm cells (23 chromosomes). -​ A mature sperm cell is called a spermatozoon. -​ These cells are relatively small (compared to eggs). -​ They are motile, as they have a flagellum and flatten head that allow the cells to propel forward. -​ Occurs in the testes. -​ Two divisions produce 4 spermatids. -​ Spermatids mature into sperm (spermatozoon). -​ Males produce about 250,000,000 sperm per day -​ By the end, cytoplasm equally divides in cells but cytoplasm is lost from the head and a flagellum develops for mobility. Oogenesis: -​ One parent diploid cell (46 chromosomes) produces one haploid ovum cell (23 chromosomes) and 2 polar bodies. -​ Through unequal cytokinesis, the ovum takes more cytoplasm, resulting in smaller polar bodies, which cannot be fertilized and disintegrate. -​ A mature egg cell is called an ovum. -​ Occurs in the ovaries. -​ Two divisions produce 2/3 polar bodies that die and 1 egg. -​ Polar bodies die because of unequal division of cytoplasm. -​ Immature egg is called an oocyte. -​ Starting at puberty, one oocyte matures into an ovum (egg) every 28 days. Mitosis Vs. Meiosis  Nondisjunction: - Occurs when: ​ 1) two homologous chromosomes move to the same pole during Meiosis I ​ 2) two sister chromatids don’t separate and move to the same pole during Meiosis II - Produces gametes with 22 or 24 chromosomes instead of 23 chromosomes in each - Meiosis, like all processes of the body, is not immune to errors and variation in outcomes. -​ Nondisjunction can occur in Anaphase I, when two homologous chromosomes move to the same pole during meiosis. -​ Nondisjunction can also occur during Anaphase II, if the sister chromatids fail to separate from each other. -​ In both cases, this results in gametes with either an extra chromosome or missing a chromosome. Aneuploidy: -​ Aneuploidy = an abnormal number of chromosomes -​ Monosomy : Only one chromosome instead of a homologous pair -​ Trisomy : Three homologous chromosomes instead of a pair -​ Monosomy is a condition in which an individual has only one homologue of a specific pair of homologous chromosomes. -​ Polysomy is a condition in which an individual has three or more of a specific chromosome. -​ Trisomy is the most common type of polysomy. -​ Trisomy describes when an individual has three copies of a chromosome (rather than a homologous pair). -​ The zygote (new cell formed from a sperm & egg) has an extra chromosome. -​ Depending on the chromosome, this will result in a variety of conditions. Down Syndrome: -​ The most common type of trisomy. -​ Most commonly it is as a result of meiotic nondisjunction in the female parent, and is associated with increased age of the female parent. -​ In Canada, 1 in 750 people are born with an extra chromosome 21. -​ This genetic difference results in a condition called Down Syndrome. -​ People with Down Syndrome inherit the physical appearance of their biological parents, while also having a characteristic facial appearance and shorter stature. Klinefelter Syndrome: -​ Trisomy 23 (47, XXY) -​ This condition is a result of a trisomy of the sex chromosomes. -​ They received an extra X chromosome from a biological parent. -​ Occurs in 1/500 to 1/1000 births. -​ People born with this condition are born with male sex characteristics (penis, smaller testes).  -​ Results in lower production of testosterone and higher production of estrogen during fetal development and at puberty. -​ They may not produce as much body hair, may have some breast development, and may produce little to no sperm. -​ Most people with Klinefelter Syndrome identify as men, and may choose to supplement their testosterone production at puberty and onward. Triple X Syndrome (47, XXX): -​ Trisomy 23 (47, XXX) -​ This condition is a result of a trisomy of the sex chromosomes. -​ They received an extra X chromosome from a biological parent. -​ Occurs in 1/1000 births. -​ People with Triple X Syndrome often experience no symptoms, or very mild symptoms. -​ Some people may experience some intellectual or learning disabilities. -​ A very small percentage may experience seizures and/or kidney disorders. -​ Most people with Triple X Syndrome identify as women. Turner Syndrome: -​ Monosomy 23 (45, XO) -​ This condition is a result of a monosomy of the sex chromosomes. -​ Occurs in approx 1/2000 births. -​ Characteristics may include short height, improperly developed ovaries, webbed neck, thyroid conditions and heart defects. Chromosomal Structure Rearrangements: -​ Structural rearrangements in chromosomes, include partial duplications, deletions, inversions, and translocations. -​ They tend to occur during prophase 1 when homologous pairs align (i.e. during crossing over). -​ Duplications and deletions often produce offspring that survive and exhibit atypical physical and mental outcomes. Diagnosing Nondisjunction: -​ In the first trimester of pregnancy, tests called Enhanced First Trimester Screening (eFTS) are completed. -​ eFTS is an ultrasound and blood work that looks for markers that increase the possible risk of Down syndrome (trisomy 21) and Edwards syndrome (trisomy 18). -​ In the first trimester of pregnancy, a blood test can be done called Noninvasive Prenatal Testing (NIPT) -​ Looks for genetic “markers” in fetal DNA that is circulating in the pregnant person’s blood. -​ More accurate test than eFTS testing. -​ Only covered by OHIP for people who meet specific criteria (e.g. positive eFTS) - meaning it costs money ($500) for most. -​ After positive eFTS and/or NIPT testing, amniocentesis is available, at the beginning of the second trimester. -​ It’s a higher risk test, as it requires drawing fetal cells from the amniotic sac (increases risk of infection). -​ This test can provide definitive diagnosis for a variety of genetic and chromosomal conditions. Genetics and Inviability: -​ Errors in genetic replication, or during meiosis or early mitosis in embryos can result in inviability. -​ One in four of all pregnancies end in miscarriage. -​ These types of errors in genetic replication are the most common cause of miscarriage. Lesson #5 Early Ideas About Hereditary: -​ Have you ever mixed two different colors of paint and made a new color? -​ Long ago, people thought that an organism’s characteristics, or traits, were determined in the same way that paint colors can be mixed. -​ The theory was that if you crossed two plants with different characteristics, the offspring would be a combination of those two combinations. This is known as the “Blending Model” and it was incorrect and oversimplified inheritance. What is Hereditary? -​ Heredity is the passing of traits from parents to offspring. -​ During the 1800s, Mendel studied genetics by doing controlled breeding experiments with pea plants.  -​ Pea plants were ideal for genetic studies because: ​ 1) They reproduce quickly. Mendel was able to grow many plants and collect a lot of data ​ 2) They have easily observable traits (such as flower color or pea shape) ​ 3) Mendel could control which pairs of plants reproduced. Pollination in Pea Plants: -​ To observe how a trait was inherited, Mendel controlled which plants pollinated other plants. -​ Pollination occurs when pollen lands on the pistil of a flower. -​ Sperm cells from the pollen then fertilize egg cells in the pistil. -​ Self-pollination occurs when pollen from one plant lands on the pistil of a flower of the SAME plant. -​ Cross-pollination occurs when pollen from one plant reaches the pistil of a flower on a different plant. -​ Mendel lets some groups of pea plants self-pollinate. With another group, he cross-pollinated the plants himself. He removed the anthers (pollen-producing part) beforehand. True Breeding Plants: -​ Mendel began his experiments with plants that were true-breeding for the trait he would test. -​ When a true-breeding plant self-pollinates, it ALWAYS produces offspring with traits that match the parent plant. -​ For example, when a true-breeding pea with wrinkled seeds self-pollinates, it produces plants with wrinkled seeds. First Generation Crosses: -​ When mendel crossed a true-breeding white and a true-breeding purple together - all of the offspring were purple. -​ Questions arose… Where did the white flower go??? Why weren’t they pink flowers? -​ Mendel’s first generation (F1) purple flowers are called hybrids. Second Generation Crosses: -​ When Mendel crossed two of the hybrid (F1 ) purple flower plants, some of the offspring were white. -​ The trait that disappeared in the first generation always appeared in the second-generation (F2). -​ Mendel got similar results each time he cross-pollinated true-breeding green seed plants with true-breeding yellow seed plants. -​ The missing trait always appeared in the second generation (F2) -​ Mendel saw these same patterns with each experiment. More Hybrid Crosses: -​ Mendel cross-pollinated many hybrid crosses. -​ He analyzed all the data and noticed all of the patterns. -​ In the crosses between hybrid plants with purple flowers to white flowers the ratio was about 3:1. -​ He concluded that two factors control each inherited trait. -​ He proposed that when organisms reproduce, the sperm and the egg each contribute one factor for each trait. -​ He hypothesized that the all purple hybrid offspring had one genetic factor for purple flowers and one genetic factor for white flowers, but somehow the genetic factor for white flowers was masked in the F1. Alleles: -​ Alleles are the different forms of a gene. -​ The alleles are located in the same position on each pair of homologous chromosomes. Dominant and Recessive Traits: -​ An allele that blocks another allele is called a dominant trait. Mendel used capital letters to show dominant traits. -​ A dominant trait, such as purple pea flowers, is seen when offspring have either one or two dominant alleles. An allele that is blocked by the presence of a dominant allele is called a recessive trait. Mendel used lower case letters to show dominant traits. -​ A recessive trait, such as the white pea flowers, is seen only when two recessive alleles are present in -​ offspring.  -​ The law of segregation states that each parent has two alleles for each gene, and passes one of those alleles at random to their offspring. Genotype and Phenotype: -​ Genotype describes the genetic makeup (combination of alleles) of an individual. -​ Phenotype describes how the genes are expressed in an individual (how they appear). -​ Complete dominance refers to the form of inheritance in which a dominant allele completely masks a recessive allele. -​ Homozygous – having identical alleles (one from each parent) for a particular characteristic, eg. AA or aa -​ Heterozygous – having two different alleles for a particular characteristic, eg Aa -​ Dominant – the allele that masks or the expression of an alternate allele; the trait appears in the heterozygous condition. -​ Recessive – an allele that is masked by a dominant allele; does not appear in the heterozygous condition, only in homozygous. -​ Monohybrid cross: a genetic cross involving a single pair of genes (one trait); parents differ by a single trait. -​ P = Parental generation -​ F1 = First filial generation; offspring from a genetic cross. -​ F2 = Second filial generation of a genetic cross Monohybrid Crosses: -​ Parents differ by a single trait. -​ Crossing two pea plants that differ in stem size, one tall one short -​ T = allele for Tall -​ t = allele for dwarf -​ TT = homozygous tall plant -​ t t = homozygous dwarf plant Punnett Square: -​ The probabilities of outcomes for the F1 generation of a cross between a “true breeding” or homozygous dominant tall plant (TT) and “true  breeding” homozygous recessive short plant (tt) Mendel’s Principles: -​ 1. Principle of Dominance: If one allele masks another, that allele is dominant over the other. This was shown by the F1 heterozygotes all having the dominant phenotype -​ 2. Principle of Segregation: When gametes are formed, the pairs of alleles become separated, so that each gamete (egg/sperm) receives only one kind of allele. -​ 3. Principle of Independent Assortment: “Members of one allele pair segregate independently from other allele pairs (on other chromosomes) during gamete formation” Test Cross: -​ To determine the genotype of an individual -​ Test cross: Cross with a homozygous recessive individual. -​ a plant with purple flowers can either be PP or Pp… therefore, you cross the plant with a pp (white flowers, homozygous recessive) -​ P ? × pp Sickle Cell Disease:  -​ Some medical conditions, like Sickle Cell Disease and Cystic Fibrosis, are controlled by complete dominance. -​ This means that a person must inherit a recessive allele from each parent in order to develop the medical condition. -​ How would two healthy biological parents produce offspring that have sickle cell disease? -​ If two biological parents with a healthy phenotype, but with a heterozygous (Aa x Aa) genotype reproduce, then they have a 25% chance of producing offspring with SCD (aa - homozygous recessive). -​ These parents are called “carriers” - they are carrying the allele for SCD, but it’s masked. -​ Red blood cells are incredibly specialized cells. -​ They contain a specific protein called hemoglobin, that carries oxygen in the cell, to be delivered throughout the body. -​ Their extremely flexible structure allows the red blood cells to travel down capillaries with widths narrower than the cell itself. -​ When someone has the homozygous recessive genotype (aa), then their red blood cells will form a sickle shape when the cell is under stress and/or in low oxygen conditions. -​ This makes the red blood cell inflexible, and unable to navigate narrow capillaries. Symptoms of Sickle Cell Disease: -​ The sickled red blood cells then block blood vessels throughout the body, which leads to many serious health symptoms: -​ Anemia (the blood doesn’t carry oxygen well) -​ Pain crises in the abdomen, chest and joints -​ Swelling in the hands and feet -​ Frequent infections -​ Vision problems -​ Delayed growth or puberty -​ Exhaustion & lethargy Lesson #6 Dihybrid Crosses: -​ The definition of a dihybrid cross is a cross between two individuals  that differ in two traits of particular interest, to see the probability of the offspring inheriting these traits. -​ Matings that involve parents that differ in two genes (two independent traits). -​ In the example we are investigating, the parent 1 is RRYY homozygous dominant (genotype), and produces round, yellow peas (phenotype) -​ The parent 2 is rryy homozygous recessive (genotype), and produces wrinkled, green peas (phenotype). -​ The results are as follows: Review: Lesson #7 Incomplete Dominance: -​ The hybrid (heterozygous) offspring displays a THIRD Phenotype!! Neither trait is completely dominant, as a result, there appears to be a blending phenotype. -​ What is the probability of white flowers if pink flowers are bred with pink flowers? -​ With a little tweaking, Mendel’s model can still be used to predict the offspring of crosses for alleles that show incomplete dominance. -​ Example: Snapdragon flowers Codominance: -​ In this pattern, the heterozygous genotype expressed both alleles equally. -​ Rather than blending or mixing, instead each district trait is shown in the phenotype of the individual. -​ There is no dominant or recessive trait. -​ Both traits are dominant, and show up in the phenotype together. Blood Type: -​ Red Blood cells can either have a glycoprotein on their surface or not. -​ The presence of a glycoprotein (I) is dominant to the absence of a glycoprotein (i). -​ Additionally, there are two types of glycoproteins that may exist on the surface of RBCs called A (IA) and B (IB). -​ Cell surface carbs A and B are codominant, which means they could also show up at the same time on a RBC -​ One blood type gene has three alleles: ​ - ​IA, IB and i -​ Alleles IA and IB are codominant -​ Allele i is recessive -​ The different glycoprotein markers on their surface are a form of antigen. -​ Antigens allow the body’s immune system (i.e. white blood cells) to recognize and identify its own red blood cells. -​ Common carbs/antigens are A and B.  -​ Different combinations of these antigens result in different blood types. -​ Another antigen of clinical significance is D antigen. -​ The Rhesus factor (Rh) is a protein that can be present on the surface of the red blood cells, which expresses D antigen. -​ + / Rh+ = presence of D antigen -​ - / Rh- = absence of D antigen -​ Along with antigens on the surface of red blood cells, the body contains specific antibodies dissolved in the blood. -​ These antibodies attack foreign blood types (i.e. Type A blood has Anti-B antibodies). -​ These antibodies bind to foreign blood and cause the blood to clump together. -​ Type O- blood is a universal donor, meaning anyone can receive this blood type in a transfusion. -​ Type AB+ blood is a universal recipient, meaning people with this blood type can receive any other -​ blood types in a transfusion. Blood Transfusions and Rh Pregnancy Complications: -​ Blood transfusions with the inappropriate blood type causes agglutination (systemic blood clumping), hemolysis (destruction of transfused blood) and potentially death. -​ A concern when a pregnant person is Rh- while their fetus is Rh+ -​ The parent may develop anti-Rh antibodies, if their blood comes in contact with their baby’s blood. -​ If the Rh- parent produces anti-Rh antibodies, then their next pregnancy is at risk if these new antibodies reach the Rh+ fetus. -​ A patient who is Rh- can produce anti-Rh antibodies, which can cause the blood of the baby in the second pregnancy to agglutinate. -​ Rh immunoglobulin (Rhlg) is a medication that stops the body from making Rh antibodies if it has not  already made them. -​ This can prevent severe fetal anemia in a future pregnancy. RhIg is given as an injection (shot). Blood Codominance Problem: -​ Human blood type is determined by both codominance and complete dominance. -​ What are the possible genotypes and phenotypes of the offspring if an individual with heterozygous A type blood reproduces with an individual heterozygous type B blood? Lesson #8 Polygenic Traits: -​ Hair, skin and eye colour, hair texture and height are all examples of incomplete dominance inheritance patterns in humans. -​ However, it’s not as simple as the snapdragon flower colours. -​ These traits are called “polygenic traits”. -​ Polygenic traits are controlled by the expression of many different genes, sometimes on many different chromosomes. -​ Primarily, these genes control the production of melanin, a chemical produced by the body that leads to darker tones of skin, eyes and hair. -​ Though controlled by many genes, melanin production is an example of incomplete dominance. -​ People who inherit more dominant alleles (i.e. melanin-producing genes), will express the dominant phenotype (i.e. darker pigmentation). -​ People who inherit more recessive alleles (i.e. non melanin-producing genes) will express the recessive phenotype (i.e. lighter pigmentation). -​ People who inherit various combinations of dominant and recessive alleles will express an intermediate phenotype (i.e. medium pigmentation) -​ These human polygenic traits are determined by multiple genes on different chromosomes, and interactions between these different alleles.  -​ The additive effects of all these different genes interacting results in a lot of variety between phenotypes, even between siblings. Sex Chromosomes: -​ They are called the “sex chromosomes” because they contain the genes responsible for sex determination. -​ However, the X and Y chromosomes contain many other genes for traits seemingly unrelated to sex determination and sexual development. -​ Science illustrations representing the Y chromosome are often very unrealistic. -​ In reality, the important difference between the X and Y chromosomes is their relative size. -​ The Y chromosome is much smaller, and therefore contains less DNA and fewer genes. -​ People with a Y chromosome have only one allele for some traits, rather than two. -​ Colour deficiency conditions affect a person’s ability to distinguish between some or all colours. -​ People with colour deficiency conditions aren’t able to perceive as many colours in the visible light spectrum. -​ As is common in biology, there are various types and causes. -​ The most common is called “red-green colorblindness”. Sex-Linked Traits: -​ Red-green colourblindness is known as a “sex-linked trait”. -​ The gene that controls the development of photoreceptors in the eyes that differentiate between red, yellow and green is located on the X chromosome. -​ Remember that all people have at least one X chromosome. -​ Red-green colourblindness is a recessive trait, controlled by a complete dominance inheritance pattern (like Mendel’s peas), however, the gene only appears on the X chromosome. -​ This means that people with XY chromosomes only have 1 allele for this gene, while people with XX chromosomes have 2 alleles. -​ Someone with XX chromosomes would have to acquire 2 recessive alleles for red-green colourblindness, one from each biological parent. -​ This means that it’s much less common for people with XX chromosomes to have this condition. -​ People with Turner Syndrome are also more likely to have red green colourblindness. This is because (due to nondisjunction during meiosis), the person only has one X chromosome. Genotype = XbO Pedigrees: -​ A pedigree chart is a graphic representation of a family tree that presents patterns of inheritance for a single gene. -​ It’s a specialized graphic organizer used to track one specific trait. Types of Traits: -​ Autosomal = A trait that is located on one of the first 22 homologous chromosomes. -​ X-linked = A trait that is located only on the X chromosome -​ Y-linked = A trait that is located only on the Y chromosome. -​ An autosomal recessive trait requires both recessive alleles in order to appear in the phenotype. -​ Appears in both sexes with equal frequency.  -​ Traits tend to skip generations. -​ When both parents are heterozygous (Rr), then approximates 1/4 of the offspring will be affected (*recall Punnett squares) Cystic Fibrosis: -​ An example of an autosomal recessive trait that can be tracked via a pedigree is Cystic Fibrosis. -​ This inherited condition affects cells that produce secretion, like mucus, sweat and digestive juices. -​ Most often due to a genetic mutation in the CFTR gene, so these mucus secretions can’t be cleared out of the respiratory tract effectively, impacting breathing and digestive processes. -​ The Cystic Fibrosis transmembrane conductance regulator (CFTR) gene is located on chromosome 7. -​ Everyone has two copies of the CFTR gene, which are inherited from each parent (recall homologous chromosomes). -​ Cystic fibrosis is an autosomal recessive trait. -​ Someone must inherit 2 alleles that contain the mutation, one -​ from each parent to be affected by cystic fibrosis Huntington's Disease: -​ An example of an autosomal dominant trait that can be tracked via a pedigree is Huntington’s Disease. -​ This inherited condition is a progressive brain disorder, which affects movement, mood and thinking skills. It’s caused by a repeated duplication mutation. -​ The Huntington’s Disease (HTT or HD) gene is located on chromosome 4. -​ Everyone has two copies of the HTT gene, which are inherited from each parent (recall homologous chromosomes). -​ Huntington’s Disease is an autosomal dominant trait. -​ Someone only has to inherit 1 allele that contains the mutation, from either parent to be affected by Huntington’s Disease. Duchenne Muscular Dystrophy: -​ People with Duchenne muscular dystrophy (DMD) experience progressive loss of muscle. -​ This is due to a mutation in the gene that encodes the muscle protein called dystrophin. -​ Because this trait is a recessive condition, an XX individual with 2 alleles must inherit one from each parent. -​ Because people with XY chromosomes only carry one copy of the allele, they are at higher risk. Evolution Lesson #1​ The Tree of Life: -​ All living things share a common ancestor. -​ We can draw a Tree of Life to show how every species is related. -​ Evolution is the process by which one species gives rise to another and the Tree of Life grows -​ The term Biological Diversity refers to the variety of living things that inhabit our planet What is a Theory? -​ People often use the word “theory” to indicate that a thought or idea is simply an opinion, and is not supported by facts or evidence -​ But a “theory” in a science class setting is much different -​ Scientific theory:​ a) an explanation that is based on observation, experimentation and reasoning​ b) it is supported by a large quantity of evidence​ c) it does not conflict with existing experimental results What is Evolution and the Theory of Evolution: -​ Evolution means “change over time” -​ Evolution is the process by which modern organisms have descended from ancient organisms -​ Evolutionary Theory: the collection of scientific evidence and facts that attempt to explain the diversity of life on Earth -​ It provides an explanation of how species change over time. -​ It suggests that modern species came to be as a result of changes to the heritable information passed on from one generation to another -​ It explains that all life on Earth shares a common ancestor -​ From Classical times until long after the Renaissance, species were considered to be special creations (from God), fixed or immutable for all time. -​ people thought the earth was less than 10 000 years old and thought it was relatively unchanging -​ Around 1800, scientists began to wonder whether species could change or transmute. -​ Lamarck thought that if an animal acquired a characteristic (adaptation) during its lifetime, it could pass it onto its offspring. Hence giraffes got their long necks through generations of straining to reach high branches. Theories of Geology: -​ Geologists such as Hutton and Lyell challenged the idea that earth was young based on geologic observations -​ studied rock formations, erosion and sedimentation rates and concluded that it must have taken millions, not thousands of years for rock formations to be made -​ evidence supported the theory of uniformitarianism - earth was formed by slow moving processes that are still at work today Evidence of Fossils and Strata: -​ Geologist William Smith and naturalist Georges Cuvier were studying fossils and showed that different species existed in the past compared with today. Evidence - Darwin’s Voyage: -​ From 1831-1836, a young naturalist called Charles Darwin toured the world in HMS Beagle. -​ He was dazzled by the amazing diversity of life and started to wonder how it might have originated Darwin’s Theory of Evolution: -​ Charles Darwin was born in 1809 in the West Midlands of England. -​ He was a naturalist, geologist and biologist. -​ He is most recognized for his 1859 book On the Origin of Species. It was so influential that in just over 10 years, the theory of evolution was accepted as fact in the scientific community. Darwin with Naturalism and Imperialism: -​ Like many naturalists of the time, Charles Darwin participated in colonial missions during the era of imperialism. -​ European naturalists, geologists and ethnologists (people who study societies and cultures), would accompany survey expeditions. -​ These expeditions would survey land in the colonies, produce maps, collect information about cultures, and identify valuable resources. -​ This information would be used as a tool for the continued imperial expansion, military campaigns, and resource extraction by European empires.  HMS Beagle: -​ In 1831, Charles Darwin was invited to be the crew naturalist on the HMS Beagle, a surveyor ship. -​ For the following 5 years, the Beagle surveyed the coast of South America. -​ Darwin’s role was to explore the continent and islands, observing flora, fauna, and geology and collecting species. -​ During his trip on the HMS Beagle, he began to notice something very interesting: -​ Species vary immensely across the globe and some areas had unique organisms not found anywhere else. -​ He also noticed that species living in very similar habitats in different parts of the world looked and/or acted very similarly. -​ He also observed that there was significant species variety in local communities. -​ Related animal species that occupy different habitats within a local environment have different features. -​ Commonly known as “Darwin’s Finches”, he observed that finches on different islands within the small Galapagos region had very different beak shapes. Fossil Records: -​ Darwin also observed that species varied over time, based on the fossils he found. -​ For example, he found* the skull of a Megatherium (an extinct giant sloth, that would have been the size of an elephant) on the Argentinian coast near Buenos Aires. -​ He concluded that contemporary species must have evolved from these ancient ancestors. -​ While on the HMS Beagle, Darwin read Lyell’s recently published book, Principles of Geology. -​ He observed the geological process that Lyell described, like gradualism. -​ He found* marine animal and shell fossils that were in land that had previously been underwater, and were now 12,000 feet above sea level, due to gradual movements of the Earth’s crust over time. Lesson #2 The Voyage of the HMS Beagle -​ In 1831, Charles Darwin completed his college studies and joined the crew of the HMS Beagle as a naturalist. He set sail on a 5-year trip around the world -​ On this voyage, Darwin would make observations and collect evidence that would lead him to propose his theory of evolution about the way life changes over time  -​ Whenever the beagle would anchor, Darwin would go ashore and collect samples of the flora and fauna. He also collected fossils of organisms that no longer lived on Earth -​ While Darwin was at sea, he spent lots of time reading the latest scientific books. -​ He studied his ever-growing collections of specimens and filled notebook after notebook with his thoughts and observations about life on earth Patterns of Diversity: 1.​ Darwin made the observation that many of the plants and animals he observed were extremely well suited to their environment. For example, he noticed that adaptations seen in desert organisms would not be seen in organisms living in a forest 2.​ Adaptations: characteristics of organisms that enhance their survival and reproduction in specific environments 3.​ These observations caused Dartwin to speculate and ponder upon several questions”​ a) why do organisms exhibit certain adaptations?​ b) why is there such a variety of ways of reproducing?​ c) why do organisms live where they do? Fossils: -​ A fossil is a preserved remains of an ancient organism -​ Darwin was an avid collector of fossils. Some of the fossils resemble organisms that were still alive, while others were unlike any creature he’d ever seen -​ Studying fossils led to even more questions:​ 1. Why have so many animals become extinct?​ 2. How were the species seen in fossils related to living species? -​ Darwin noted the similarities and differences between many different organisms. He became convinced that organisms had changed over time The Galapagos Islands: -​ The galapagos islands are a small cluster of islands located off the west coast of south america -​ The cluster of islands that compose the galapagos islands is close together but they have very different climates. The lower islands in the group are hot, dry and nearly barren. The higher islands have greater rainfall and rich vegetation -​ It was clear to Darwin that the organisms found on each island had special adaptations that allowed them to survive only on that island. Adaptations that allowed for survival on one island would not be helpful on a different island -​ Darwin was particularly interested in the large land tortoise of the galapagos -​ He could easily tell which island a turtle lived on by their shell. The hood island tortoise has a long neck, and a shell that is curved and open around the legs. This allowed the tortoise to reach up high to feed upon the sparse vegetation -​ The isabela island tortoise has a dome-shaped shell and a short neck -​ Isabela island had abundant vegetation that grows close to the ground  -​ Tortoises from pinta island have a shell that is intermediate between the two forms -​ It was clear to darwin that the turtles were adapted to their own environment The Journey Home: -​ While heading home, Darwin spent most of his time studying his collections of organisms and making observations. Darwin began to wonder if animals living on different islands had once been members of the same family -​ Darwin began to hypothesize that separate species evolved from ancestral species after becoming isolated from one another. -​ However, many people found Darwin's ideas too shocking to accept. Reasons why many people found darwin's work unacceptable include:​ 1. Many people in Darwin’s day believed that the Earth was only a few thousand years old -​ They believed that the Earth and all of its lifeforms had been created only a few thousand years ago too​ 2. It was believed since the creation of Earth and its life forms, neither the planet nor its living species had undergone any changes​ 3. It was believed that rocks and and major geological features had been produced suddenly, by catastrophic events that humans rarely witnessed The Earth is Ancient and Changing: -​ During Darwin’s time, scientists were examining and studying the features on Earth in great detail. They began to study rock layers called strata. The data they collected suggested that the Earth was very old and had changed slowly over time -​ Several scientists who formed important theories about the changes on Earth greatly affected and influenced Darwin The Foundations of Evolution: Theory and Credited Main Idea(s) Researcher Paleontology and 1. Cuvier was a pioneer in paleontology, the study of fossils. He collected Catastrophism​ fossilized bones and spent years reconstructing the appearance of these ​ animals. He collected convincing evidence that these fossils were very George Cuvier (1769 - 1832) different from any living species​ ​ 2. Cuvier discovered that deeper and older strata contain fossils that are increasingly different, he noted that the older the strata the older and more different the fossil. He also discovered many “sudden changes” in the kinds of fossils found in one stratum compared to the next​ ​ 3. Cuvier’s hypothesis was termed “Catastrophism” 4. Catastrophism: The principle that events in the past occurred suddenly and  were caused by different mechanisms than those operating today, in other words catastrophes in the past (such as a flash flood or volcanic eruption) were responsible for destroying certain species Gradualism​ In 1795, James Hutton published a detailed hypothesis about the geologic ​ forms that have shaped Earth​ James Hutton (1726-1797) His hypothesis covered the following ideas:​ ​ a) layers of rock form very slowly​ b)some rocks are moved up by forces beneath the Earth’s surface to form mountains​ c) Mountains and valleys are shaped by natural forces d)these processes occur very slowly and over millions of years Uniformitarianism​ Lyell’s Idea was called “Uniformitarianism” ​ ​ Principle of uniformitarianism: The mechanisms of change are uniform over Charles Lyell (1797 - 1875) time. The same geological forces that were active in the past are still operating today This new understanding of geology affected darwin in two ways: 1.​ Darwin wondered that if the earth could change slowly over time, then could living organisms on earth also change slowly over time? 2.​ Darwin realized that in order for life to change over time, the earth would have to be extremely old Theory of Acquired Lamarck was one of the first scientists to propose that living organisms had Characteristics​ changed over time John-Baptise Lamarck (1744 In 1809, lamarck published his hypothesis known as the “Theory of Acquired - 1829) Characteristics”, which stated that individuals acquire traits during their lifetime as a result of their experience or behaviour, then pass these traits to their offspring In other words, if you spend your entire life lifting weights and building muscle, your children will have big muscles too, or if you lose a finger in an accident your child will have one less finger Although Lamarck’s theory was quickly rejected, it was important for several reasons:​ a) Lamarck was the first to recognize that organisms changed over time​ b) He was the first to develop a hypothesis about evolution c) he was one of the first to recognize that organisms are adapted to their environment  Human Population Issues​ In a book published by Malthus which discussed his thoughts about human ​ population growth, he noted that human babies were being born faster than Thomas Malthus (1766 - people were dying 1834) He reasoned that if the human population continued to grow at such a rapid rate, eventually there would not be enough space or food to support the population. Darwin realized that these ideas applied even more strongly to plants and animals. Darwin knew that a plant might produce thousands of seeds, but that every single seed did not result in a new plant, and those that did grow had a small chance of reproducing themselves. Darwin Develops his Theory of Evolution: -​ Darwin arrived back in england in 1836, and he wouldn’t publish his own work until 1859 -​ Once back Darwin began to study the fossils and specimens that he had collected, and filled notebook after notebook on the diversity of life on earth and how it had evolved over time -​ Adaptations are characteristics of organisms that enhance their survival and reproduction skills in specific environments -​ Darwin explained that organisms become “adapted” by natural selection -​ According to Darwin, natural selection is a process by which individuals with certain inherited traits leave more offspring than individuals with other traits -​ Darwin was reluctant on publishing his ideas due to the fact that it challenged fundamental scientific and religious beliefs -​ In 1858, Darwin received a letter from Alfred Russel Wallace, in his letter, Wallace summarized his thoughts on evolutionary change and was too similar to Darwins. Darwin realized that he must quickly publish his work. Eighteen months later in 1859, darwin published his book “On the origin of species by means of natural selection” Descent with Modification: -​ In his book, Darwin discusses descent with modification -​ By using this term, Darwin hypothesized that all organisms descended from a common ancestor -​ While in the Galapagos, Darwin inspected 13 different types of finches. Each species has a different beak that is adapted to acquiring a very specific type of blood -​ Darin thought that all 13 species descended from a common ancestor, and through millions of years their ancestors accumulated “modifications” or adaptations that made them “fit” to a specific environment Artificial Selection: -​ Artificial Selection: variations exist in plants and animals. By selective breeding, humans select the variations they find to be most useful  -​ Darwin noted that plant and animal breeders were aware of the variations that existed in living organisms, and through selective breeding they could improve their crops and livestock -​ Selective breeding is a method of breeding that allow only those individual organisms with desired characteristics to be produced next generation -​ Darwin noted that farmers would routinely selected for breeding only the largest hogs, fastest horses or trees bearing the most fruit Concepts of Evolutions by Natural Selection: Concept #1 Organisms mate with and reproduce like organisms. There is a stability in the process of reproduction Concept #2 In any given population, there are chance variations among individual organisms. Some of these variations are passed to future offspring Concept #3 The “struggle for existence” of members of a species for food, water, living space, etc. for example, the predators that are faster and have longer claws will likely catch more prey, and prey that are faster or better camouflaged live longer Concept #4 The number of individuals that survive and reproduce in each generation is small compared to the number that us born/produced Concept #5 Which individuals will survive and reproduce and which will not is determined by how well suited an organism is to its environment, which Darwin calls “fitness” Concept #6 Fitness is the result of adaptations. An adaptation is any inherited characteristics that increase an organism's chance of survival Concept #7 Individuals with characteristics that are not well suited to their environment either die or leave few offspring Concept #8 Individuals with characteristics well suited to their environment survive and reproduce more successfully, passing these favourable traits onto the next generation. This became known as “survival of the fittest”​ ​ This is the process that Darwin calls natural selection, The process in which individuals with certain favourable traits leave more offspring than individuals with other traits Lesson #3 Natural Selection: -​ The few that survive in each generation are those with the traits best suited for survival in that specific environment. -​ The survivors then reproduce, and pass on their advantageous traits to their offspring. -​ The organisms that didn’t survive don’t pass the disadvantageous traits onto future generations. -​ Each new generation has a higher proportion of individuals with advantageous traits. Survival of the Fittest: -​ Darwin defined the “fitness” of an individual as its ability to survive and reproduce in its specific environment. -​ Certain adaptations make individuals of a species better suited for an environment. -​ Individuals with adaptations that increase their fitness survive and reproduce most successfully, passing those traits on. -​ Natural selection does not make organisms “better”. Survival of the fittest doesn’t mean the survival of the strongest, fastest, or most intelligent. -​ Organisms that are more able to adapt and respond to changes in their environment are most likely to survive. -​ These adaptations simply enable an organism to pass on their genes to the next generation. Important Points on Natural Selection: 1.​ Individuals do not evolve, a population evolves over time 2.​ Natural selection can amplify or diminish inheritable traits 3.​ Environmental factors vary from place to place over time, a trait that is favoured in one place may be useless, or harmful in another place The Evidence of Evolution: -​ Darwin argued that life on Earth had been changing and evolving for millions of years. The following areas provide evidence for evolution​ 1) The fossil records​ 2) The geographic distribution of living organisms​ 3) Homologous body structures​ 4) Embryology​ 5) Biological Molecules The Fossil Record: -​ Fossil: A fossil is the remains of an organism that died long ago -​ Fossils provide the strongest evidence of evolution, and that past organisms differed from present day organisms -​ Scientists seek to find both the “relative age” and the “absolute age” of a fossil  -​ The relative age of a fossil is the age of an object in relation to the ages of other objects. For example, when scientists study rock layers or strata, the deeper the fossil the older it is, and the higher the fossil the younger it is -​ Absolute age of a fossil is the actual age of the fossil given in years, it is determined through radioactive data processes -​ Fossils contain radioactive isotopes that have a half-life, the age can be determined by measuring the amount of isotope it contains What is Learned from Fossils? a)​ Different organisms lived at different times b)​ Today’s organisms are different from the ones in the past c)​ Fossils found in adjacent layers are more like each other than to fossils in deeper or higher layers d)​ By comparing fossils from around the world, scientists can determine when and where different species existed e)​ Fossils provide evidence about the environment in which the organism existed -​ By examining transitional fossils, scientists can determine how organisms have changed over time, -​ Transitional fossils have features and characteristics that are intermediate between ancient ancestors and their later descendants Limitations of Fossil Evidence: -​ Fossils provide limited information and don't contain soft tissue (skin, fur, hair, etc.) Biogeography: The Geographic Distribution of Organisms -​ Biogeography is the study of the location of organisms -​ It refers to the distribution of plants and animals throughout the world -​ Darwin wondered why places geographically similar had different organisms, yet when he looked at different animals in similar environments, he realized that they had similar behaviours and traits -​ He concluded that species now living on different continents had each descended from different ancestors -​ But because these organisms were facing similar ecological co