Biological Concepts

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Chapter 5 Biological Concepts
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Key Concepts

• Cells can be either prokaryotic or eukaryotic
• Prokaryotic no membrane bound organelles
• Bacteria
• Eukaryotic membrane bound organelles, more
  complex
• Protists, fungi, plants, animals
• Cells produce new cells by the process of cell
  division
• Evolution is the process by which the genetic
  composition of populations of organisms changes
  over time
• Natural selection favors the survival and
  reproduction of those organisms that possess
  variations that are best suited to their
  environment

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Key Concepts

• A species is a group of physically similar,
  potentially interbreeding organisms that share a
  gene pool, are reproductively isolated from other
  such groups, and are able to produce viable
  offspring.

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• The binomial system of nomenclature uses two
  words, the genus and the species epithet, to
  identify an organism.
• Homo sapiens or Homo sapiens - human
• Callinectus sapidus or Callinectus sapidus blue
  crab
• Common names can be confusing, the scientific
  name allows you to know the organism no matter
  what language you speak

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• Now, most biologists classify organisms into one
  of three domains, categories that reflect
  theories about evolutionary relationships.
• Phylogenetic trees and cladograms indicate
  evolutionary relationships among groups of
  organisms

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• 3 Domains of Life
• Archaea prokaryotic
• Includes extremophile bacteria
• Bacteria prokaryotic
• Includes bacteria formerly in Kingdom Monera
• Eukarya eukaryotic cells
• Inlcudes protists, fungi, plants and animals
• The numbers in Archaea and Bacteria far outnumber
  the numbers in Eukarya

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Building Blocks of Life

• Macromolecules (large molecules) are some of the
  most important chemical compounds in organisms
• 4 major classes of macromolecules in living
  organisms are
• carbohydrates
• lipids
• proteins
• nucleic acids

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Carbohydrates

• Contain C, H and O, frequently in a 121 ratio
• CH2O - thus the name carbohydrate (carbon water)

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Carbohydrates

• Sugars
• monosaccharides are simple sugars, usually with 5
  or 6 C atoms
• ribose and deoxyribes are in nucleic acids
• glucose is the basic fuel molecule for cells
• disaccharides consist of 2 monosaccharides bonded
  together
• types of disaccharides
• sucrose glucose fructose (table sugar)
• maltose glucose glucose
• lactose glucose galactose (milk sugar)

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Carbohydrates

• Polysaccharides
• these carbohydrates are polymers, large molecules
  consisting of the same basic units linked
  together
• storage forms of polysaccharides
• starches found in plants, algae, and some
  microorganisms, made of units of glucose
• glycogen, animal starch - is produced by
  animals and some microorganisms to store glucose
  for future use
• structural polysaccharides
• cellulose is found in cell walls of plants, algae
• chitin is in fungi cell walls and exoskeletons of
  some marine animals

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Lipids

• Fats, Oils Waxes
• Composed primarily of C and H
• fatty acids long hydrocarbon chains containing
  an acid group
• Triglycerides simple fats composed of 3 fatty
  acids attached to a glycerol molecule
• Functions within marine organisms
• store energy, cushion organs, buoyancy
• phospholipids are part of cell membranes
• steroids, which have complex ring structures, are
  chemical messengers, e.g., testosterone
• waxes act as a covering or water barrier

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Proteins

• Proteins are polymers of amino acids
• 20 different amino acids make up proteins
• polypeptideschains of amino acids, which are
  coiled and folded into complex, three-dimensional
  protein molecules
• Functions of proteins
• compose primary structural components of animals
  muscles and connective tissue
• enzymesbiological catalysts
• transport or store chemicals

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Nucleic Acids

• Nucleic acidspolymers of nucleotides
• Nucleotides are composed of 5-carbon sugar
  nitrogen-containing base phosphate group
• DNA RNA
• - two types of nucleic acids found in living
  organisms

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Nucleic Acids

• DNA (deoxyribonucleic acid)
• Large, double stranded, helix-shaped molecule
• sugar deoxyribose
• N-containing bases
• A adenine
• G guanine
• C cytosine
• T thymine
• DNA
• A section of DNA is called a gene (genetic
  material)
• genes code for proteins
• can copy itself so that genes can be past from
  one generation to the next

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Nucleic Acids

• RNA (ribonucleic acid)
• usually a single-stranded molecule
• sugar ribose
• N-containing base adenine, guanine, cytosine or
  uracil
• functions in protein synthesis
• messenger RNA (mRNA)
• ribosomal RNA (rRNA)
• transfer RNA (tRNA)

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Cells

• Cells are basic units of living organisms
• All cells are capable of basic processes
• metabolism
• growth
• reproduction
• Surrounded by cell membrane
• Cytoplasm, within the cell membrane is composed
  of cytosol (fluid content of cell) and organelles

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Types of Cells

• Prokaryotic cells (bacteria, archaeans)
• lack a nucleus and membrane-bound organelles
• prokaryotes (prokaryotic organisms) are always
  unicellular

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• Eukaryotic cells (protists, fungi, plants,
  animals)
• have a well-defined nucleus and many
  membrane-bound organelles
• eukaryotes may be uni- or multi-cellular

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Organelles

• Have specific functions within cell
• Nucleus
• Mitochondria
• Chloroplasts
• Endoplasmic reticulum
• Lysosomes
• vacuoles

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Energy Transfer in Cells
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Energy Transfer in Cells

• Photosynthesis
• low-energy molecules (CO2 and H2O) combine to
  form high-energy food molecules (carbohydrates)
• Primary producers perform photosynthesis
• Cyanobacteria
• Some eukaryotes do photosynthesis algae and
  plants

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Energy Transfer in Cells

• Cellular respiration
• releases energy from food molecules
• most occurs within mitochondria
• two membranes, with inner membrane folded many
  times to form mitochondrial cristae
• food molecules are broken down to create ATP and
  release CO2 as a waste product

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Cellular Reproduction

• Cell division in prokaryotes
• Bacteria only have 1 single, circular chromosome
• binary fissionchromosome is duplicated, and cell
  splits into 2 daughter cells

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Cellular Reproduction

• Cell division in eukaryotes
• Eukaryotes have multiple linear chromosomes
• depends on species
• Have to use mitosis to ensure a copy of each
  chromosome ends up in each new cell
• Process
• Chromosomes duplicate
• Mitosis
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokenesis the division of the cell

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Levels of Organization

• All living things are made up of at least one
  cell
• Prokaryotes (bacteria) are made of one cell
• Eukaryotes can be unicellular (some protists) or
  multicellular (protists, fungi, plants, animals)
• Multicellular level of organization
• Cell
• Group of specialized cells makes up a tissue
• Couple of tissues makes an organ
• Organs make up organ systems
• Organ systems make up an individual

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Evolution and Natural Selection

• Evolutionthe process by which populations of
  organisms change over time
• Evolutionary biology investigates
• how and when organisms evolved
• what role the environment plays in determining
  the characteristics of organisms that can live in
  a given area

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Darwin and the Theory for Evolution

• Voyage of discovery
• Darwin traveled on the HMS Beagle for 5 years,
  beginning in 1831
• Darwin was influenced by Charles Lyell and other
  geologists who concluded that
• since geological change is slow and continuous,
  the earth is very old
• slow and subtle changes become substantial when
  they continue for centuries/millennia

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Darwin and the Theory for Evolution

• Formulating a theory for evolution
• Darwin was inspired by Thomas Malthuss essay
  about factors that control the human population
• Darwin developed his hypothesis evolution by
  natural selection to explain why populations
  generally do not exhibit unchecked growth and how
  they change over time
• published in On the Origin of Species by Means of
  Natural Selection

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Darwin and the Theory for Evolution

• Theory of evolution by natural selection
• artificial selection is practiced by farmers and
  breeders to obtain desirable traits in
  plants/animals
• We pick our domesticated animals and crops based
  on desirable traits
• All of our domesticated species look very
  different from their ancestors
• Darwin believed a similar process was occurring
  in nature
• natural selection favors survival and
  reproduction of those organisms best suited to
  their environment

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Darwin and the Theory for Evolution

• Four basic premises of Darwins theory
• All organisms produce more offspring than can
  possibly survive to reproduce.
• There is a great deal of variation in traits
  among individuals in natural populations. Many of
  these variations can be inherited.
• The amount of resources (e.g., food, light,
  living space) necessary for survival is limited.
  Therefore organisms must compete with each other
  for these resources.
• Those organisms that inherit traits that make
  them better adapted to their environment are more
  successful in the competition for resources. They
  are more likely to survive and produce more
  offspring. The offspring inherit their parents
  traits, and they continue to reproduce,
  increasing the number of individuals in a
  population with the adaptations necessary for
  survival.

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Darwin and the Theory for Evolution

• New traits arise due to mutations in the DNA
• Mutations are random and it might take many over
  a long period of time to lead to a new trait
• an organism evolves traits that are beneficial,
  as well as traits that are neither harmful nor
  beneficial

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• Natural selection
• There will be some individuals in the population
  that have traits that make them suited for the
  environment or a change in the environment
• Those individuals will be more successful at
  finding food and surviving. This will make them
  more likely to successfully have offspring,
  therefore passing on those traits.

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• Evolution does not necessarily lead to perfection
• Environmental pressures cause advantageous traits
  to persist
• Those traits have to be present to be subjected
  to the environmental pressure
• An organism cannot wish to have a desirable
  trait. Random mutation of DNA leads to new
  traits that just might be beneficial in the
  current environment
• Also leads to traits that are not beneficial or
  harmful, they are just traits that are there

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Genes and Natural Selection

• When Darwin proposed theory of evolution by
  natural selection, cell division, genes and
  chromosomes had not been discovered.
• Modern evolutionary theory
• the modern synthetic theory of evolution is
  essentially Darwins 1858 idea refined by modern
  genetics
• genes
• produce traits when genetic information is
  translated into proteins
• can exist in different forms called alleles
• the offspring receives 1 allele for a trait from
  each parent, producing many possible combinations
  of alleles in the offspring

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Genes and Natural Selection

• Role of reproduction
• in asexual reproduction, offspring are clones of
  and identical the single parent, variation
  results from mutation only

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Genes and Natural Selection

• Role of reproduction
• in sexual reproduction, chromosomes from 2
  parents are combined
• gametes (sex cells) unite during fertilization
• gametes have a haploid number (N) of chromosomes
  instead of a diploid number (2N)
• the haploid number of chromosomes from 2 gametes
  combine to form the diploid number

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Genes and Natural Selection

• Role of reproduction (cont)
• meiosis (reduction division) is special kind of
  cell division that forms haploid cells called
  gametes

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Genes and Natural Selection

• Population genetics
• organisms must adapt to changing environmental
  conditions in order to survive
• ability to adapt is limited by the gene pool
• Only individuals that have combinations of genes
  and alleles that allow adaptations to their
  surroundings are likely to survive and reproduce
• fitness (biological success) is measured by the
  number of an organisms own genes that are
  present in the next generation

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Evolution of New Species

• Modern species definition
• a species is one or more populations of
  potentially interbreeding organisms that are
  reproductively isolated from other such groups
• Isolation leading to speciation can happen many
  different ways
• reproductive isolation members of a different
  species are not in the same place at the same
  time or are physically incapable of breeding, so
  genes from different species are not mixed
• habitat isolationsimilar species of organisms
  live apart and never encounter each other
• anatomical isolationincompatible copulatory
  organs prevent similar species from reproducing
  with one another
• behavioral isolationexhibiting of special
  behaviors during the breeding season, so that
  only members of the same species recognize the
  behavior as courtship
• temporal isolationthe time members of one
  species are ready to reproduce does not coincide
  with the time members of a related species
  reproduce
• biochemical isolationbiochemical or genetic
  differences between the gametes of 2 species
  prevent successful copulation from resulting in
  offspring

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Classification Bringing Order to Diversity

• Phylogeny evolutionary history of a species or
  group of related species
• phylogenetic tree traditional representation of
  phylogeny
• phenetics classification of organisms based on
  similar characteristics with little attention to
  when these characteristics evolved.
• cladistics bases classification on the order in
  time that the branches arise along a phylogenetic
  tree called a cladogram, ignores similarity of
  structure

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