3.28.05 - El Camino College

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Transcript 3.28.05 - El Camino College

Chapter 10: Plant Reproduction,
Growth, and Development
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Control of Plant Growth and
Development
• Since each plant cell is totipotent,
hormones have a role in determining
cellular differentiation.
• Plant Hormones
• There are five common groups of plant
hormones: auxins, gibberellins, cytokinins,
abscisic acid, and ethylene.
Effects of ethylene
Positive phototropism
Negative gravitropism
Root nodules
Mycorrhizae
Chapter 8: Photosynthesis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Radiant Energy
• Photosynthesis converts solar energy into
the chemical energy of a carbohydrate in
this way:
• Solar energy + carbon dioxide + water →
carbohydrate + oxygen
• Photosynthetic organisms include plants,
algae, and certain bacteria.
• These organisms are called producers;
they synthesize organic molecules from
raw materials.
Structure and Function of
Chloroplasts
• Chloroplasts are the cellular organelles
that carry on photosynthesis.
• Pores called stomata allow CO2 and O2 to
enter the leaf.
Structure of Chloroplasts
• The inner membrane encloses a large central space
called the stroma that houses enzymes used to reduce
CO2 to carbohydrate.
• A membranous system of thylakoids (discs) lie within
the stroma; stacked thylakoids are called: grana.
Thylakoids contain chlorophyll and other pigments to
capture light energy for photosynth!
• Chlorophyll and other pigments absorb solar energy which will
energize electrons prior to reduction of CO2 in the stroma.
Chloroplast structure
CO2 “breathed-in” through
stomata!
Solar energy + 6CO2 + 6H2O → C6H12O6 + 6O2
The light-dependent reactions: the
cyclic electron pathway
The light-dependent reactions: the
noncyclic electron pathway
ATP Production
• Each time water is split, two H+ remain in
the thylakoid space.
• As electrons move down the electron
transport system, they give up energy,
which is used to pump H+ from the stroma
into the thylakoid space.
• Thus, H+ build up in the thylakoid space.
• The flow of H+ through an ATP synthase
complex back into the stroma drives the
chemiosmotic production of ATP.
Electron transport system
The Calvin cycle (simplified)
Photosynthesis Versus Cellular
Respiration
• Both plant and animal cells carry on cellular respiration
in mitochondria; photosynthesis occurs in plant
chloroplasts.
• Photosynthesis is the building up of glucose, while
cellular respiration is the breaking down of glucose.
• Both processes occur in plant cells during daylight, but
only cellular respiration occurs in plant cells at night.
Photosynthesis versus cellular
respiration
Dr. L Humphries
[email protected]
Spring 2005: Fundamentals of Biology
Section 1107
Biology 10
4-Units
EXERCISE 14:
Angiosperm Leaf
Organization of Leaves
• Leaves are the organs of photosynthesis
in vascular plants.
• Leaves have a flattened blade, that may
be single or composed of leaflets,
attached to a petiole.
• The epidermal layers may bear protective
hairs or glands that produce irritating
substances; a waxy cuticle reduces water
loss and permits gas exchange.
Leaf structure
• Leaves are adapted to environmental
conditions and may be broad and wide or
reduced with sunken stomata.
• The leaves of a cactus are spines
attached to a succulent stem.
• Climbing leaves, such as those of peas,
are modified into tendrils.
• The leaves of a few plants are specialized
for catching insects.
Leaf diversity
Spines
(modified leaves)
Stem
(photosynthetic
and storage)
Angiosperm
(fruit/flowering)
Saguaro
(the largest cacti
in the US- 30 ft. tall, 200 yrs. old!)
Moss
(plantae)
Green Algae
(plantae)
Human
(animalia)
Lichen
(fungi)
Gymnosperm
(modified leaves!)
perm
eaves!)
Gymnosperm
(How is this tree
still alive?!?!)
Classification of leaves
Opening and closing of stomata
Dr. L Humphries
[email protected]
Spring 2005: Fundamentals of Biology
Section 1107
Biology 10
4-Units
EXERCISE 15:
Angiosperm Flower and Seed
Sexual Reproduction in Flowering
Plants
• Sexual reproduction requires gametes,
often as egg and sperm.
• In flowering plants, the structures that
produce the egg and sperm are located
within the flower.
• Flowers have special structures to enable
fertilization of egg by sperm.
Structure of Flowers
• The reproductive portions of a flower are
the stamen, consisting of a stalk-like
filament bearing an anther, and the pistil,
made up of stigma, style, and ovary.
• The ovary contains one or more ovules.
• Sepals enclose a whorl of petals that are
usually colored to attract pollinators.
Flower structure
Development of Seeds and Fruits
• In flowering plants, seeds are enclosed
within a fruit that usually develops from the
ovary.
• The ovary wall becomes the pericarp.
• Fleshy fruits have a fleshy pericarp; dry
fruits have a dry pericarp.
• An aggregate fruit such as blackberry is
derived from many ovaries on the flower.
• The ovule wall hardens and becomes the
seed coat.
• The seed consists of the sporophyte
embryo, stored food, and a seed coat.
• The ovary may develop into a fruit.
Fruit diversity
Common garden bean, a dicot
Corn, a monocot
Dr. L Humphries
[email protected]
Spring 2005: Fundamentals of Biology
Section 1107
Biology 10
4-Units
The Petri Dish: GMO
Write a one page paper on GMO’s (genetically modified organism) using the
following format. Be sure to include YOUR opinion
Please use the following format:
1st Paragraph = Intro: What is a GMO, how are they made, and who makes them?
2nd Paragraph = Name a specific type of GMO that is either currently produced or
is being researched and/or tested. (tomatoes, soybeans)
3rd Paragraph = Write AT LEAST a 5 sentence closing paragraph discussing how
YOU feel about GMOs. Would you eat them? Do you eat them? Do you think
they are safe or unsafe? If you could make one, what would it be? Etc…….
Genetic Engineering of Plants
• Various techniques introduce foreign DNA
into protoplasts that are propagated in
tissue culture.
• Adult plants are generated from these
cells and could produce insecticideresistant plants or plants that can grow in
nutrient-limited soil.
• Plants can also be engineered to treat
human diseases.
• Evolution encompasses common descent
and adaptation to the environment.
• Due to common descent, all living things
share common characteristics: they are
made of cells, take chemicals and energy
from the environment, respond to external
stimuli, reproduce, and evolve.
• Many fields of biology give evidence that
evolution has occurred.
Fossil Evidence
• Fossils are the remains of past life, usually
consisting of hard parts, such as shells,
bones, or teeth.
• Most fossils are found embedded in
sedimentary rock.
• Sedimentation causes rock formation as
particles accumulate in layers; any given
stratum (layer) is older than the one above
it, and younger than those below.
• Paleontologists are biologists who study
fossils.
• Certain fossils serve as transitional links
between groups.
• Such fossils allow paleontologists to
deduce the sequence in which certain
groups evolved (i.e., fishes evolved before
amphibians, which came before reptiles,
which evolved before both birds and
mammals).
Transitional fossils
• Geological Time Scale
• As a result of studying strata across the
earth, scientists have divided earth’s history
into eras, periods, and epochs.
• There are two ways to date fossils:
• Relative dating provides an approximate
age based on position of the fossil within
rock strata.
• Absolute dating uses radioactive isotopes to
measure the amount of radiation left in a
fossil, yielding an actual age.
• Carbon 14 (14C) is the only radioactive
isotope in organic matter.
• The amount of radioactivity remaining in a
fossil can be compared with that of a
modern sample to determine the age of a
fossil.
• Radioactive isotopes decay at a known
rate; the half-life of a radioactive isotope is
the length of time it takes for half of the
radioactive isotope to change into another
stable element.
• Mass Extinctions
• Extinction refers to the death of every
member of a species.
• During a mass extinction, a large
percentage of species become extinct
within a relatively short period of time.
• Mass extinctions occurred at the ends of
the Ordovician, Devonian, Permean,
Triassic, and Cretaceous periods.
• The Cretaceous mass extinction that led to
the demise of dinosaurs was likely caused
by an meteorite hitting the earth.
Dinosaurs
Biogeographical Evidence
• Biogeography is the study of the
distribution of plants and animals
throughout the world.
• The world’s six biogeographical regions
have their own distinct mix of living things.
• Continental drift refers to the changing
positions of the continents over time.
• Two hundred twenty-five million years ago,
all the present land masses belonged to one
continent (Pangaea).
• The distribution of plants and animals is
consistent with continental drift.
• Organisms, such as certain seed plant
groups or reptiles, are widely distributed
throughout the world.
• Other groups, such as mammals that arose
after the continents broke up, have great
differences in species on different
continents.
Continental drift
Anatomical Evidence
• Despite dissimilar functions, all vertebrate
forelimbs contain the same sets of bones
– this strongly suggests common descent.
• Structures that are similar because they
are inherited from a common ancestor are
homologous structures.
• Analogous structures are used for the
same purpose but are not due to a
common ancestor.
Bones of vertebrate forelimbs
• Vestigial structures are anatomical
features that are fully developed in one
group but reduced or nonfunctional in
other, similar groups.
• Vestigial structures can be explained by
common descent.
• The homology shared by vertebrates
extends to their embryological
development; all vertebrates have a dorsal
notochord and paired pharyngeal pouches
at some point.
• Evolution modifies existing structures.
Significance of developmental
similarities
Biochemical Evidence
• All organisms have certain biochemicals in
common.
• All use DNA, ATP, and many identical or
nearly identical enzymes.
• Organisms use the same triplet code and
the same 20 amino acids in proteins.
• This similarity is not necessary, but can be
explained by common descent.
Significance of biochemical
differences
• Once a plasma membrane formed, a
protocell could have come into existence.
• Energy for the chemical reactions could
have come from ultraviolet radiation,
volcanoes, bombardment by comets, or
from oceanic hydrothermal vents.
• The early atmosphere lacked oxygen and
also a shield of ozone; it was not until
photosynthesis evolved that oxygen was
present in earth’s atmosphere.
Origin of the first cell(s)
Evolution of Small Organic
Molecules
• Experiments by Stanley Miller in 1953
tested the hypothesis that small organic
molecules were formed at the ocean’s
surface.
• The first atmospheric gases (methane,
ammonia, and hydrogen) were placed into
a closed system, heated, and circulated
past an electric spark to simulate lightning.
• A variety of amino acids and organic acids
formed.
Miller’s experiment
Chemical evolution at hydrothermal
vents
Macromolecules
• There are three hypotheses concerning
how small organic molecules could give
rise to macromolecules:
• The RNA-first hypothesis suggests that
only the macromolecule RNA was needed
to progress toward the first cell.
• RNA molecules (as ribozymes) can
sometimes be both substrates and
enzymes.
• The protein-first hypothesis, by Sidney
Fox, suggested that amino acids collected
in small puddles, and heat from the sun
caused them to form proteinoids; when
proteinoids were returned to water, they
formed microspheres and had many
properties of cells.
• This hypothesis assumes that DNA came
after proteins.
• The third hypothesis, by Graham CairnsSmith, suggests that clay was helpful in
causing polymerization of both proteins
and nucleic acids at the same time.
• Clay attracts small organic molecules and
contains iron and zinc, which may have
served as inorganic catalysts for
polypeptide formation.
• This hypothesis suggests that RNA and
polypeptides arose at the same time.
The Protocell
• Before the first true cell, there would have
been a protocell that had a lipid-protein
membrane and used energy metabolism.
• Fox has shown that if lipids are available to
microspheres, the two form a lipid-protein
membrane.
• Other work by Alexandr Oparin has shown
that concentrated mixtures of
macromolecules form coacervate droplets
that a semipermeable boundary may form
around.
Protocell anatomy
The Heterotroph Hypothesis
• The protocell was likely a heterotroph,
absorbing small organic molecules from its
environment.
• Natural selection would favor cells able to
extract energy from carbohydrates to
transform ADP to ATP.
• Fox has shown that microspheres have
some catalytic ability, and Oparin found
coacervates incorporate available
enzymes.
The True Cell
• A true cell is a membrane-bounded
structure that can carry on protein
synthesis to produce the enzymes that
allow DNA to replicate.
• It is possible that the sequence of DNA to
RNA to protein developed in stages.
• Once the protocells acquired genes that
could replicate, they became cells capable
of reproducing, and evolution began.
Population Genetics
• A population is all the members of a
species occupying a particular area at the
same time; members of a population
reproduce with each other to produce the
next generation.
• The various alleles of all the gene loci in
all the members make up the gene pool
for the population.
• Hardy and Weinberg used a binomial
expression to calculate the genotypic and
phenotypic frequencies of a population:
• p2 + 2pq + q2 = 1
• This expression is used to determine gene
frequencies at a given time and to predict
gene frequencies in the future.
• If reproduction is completely random, the
Hardy-Weinberg equation predicts the
same gene pool frequencies generation
after generation.
Using the Hardy-Weinberg equation
• The Hardy-Weinberg Law
•
The Hardy-Weinberg law states that
gene frequencies will stay the same in a
large population over time provided:
1) There are no mutations or mutations are
balanced.
2) There is no genetic drift; changes in
allele frequencies due to chance alone
are insignificant.
3) There is no gene flow – no migration of
individuals in or out of the population.
4) Mating is random – individuals pair by
chance and not by choice.
5) There is no selection – no selective force
favors one genotype over another.
6) In real life, these conditions are rarely
met, and microevolution, as seen by
changing gene frequencies in HardyWeinberg equilibrium, occurs.
Microevolution
Five Agents of Evolutionary
Change
• Mutations
• Mutations provide new alleles and
therefore underlie all other mechanisms
that produce variation.
• Mutations alone are unlikely to cause
evolution; selective agents acting on
heritable variation cause evolution.
• The adaptive value of a mutation depends
on the environmental conditions.
• Genetic Drift
• Genetic drift refers to changes in allele
frequencies of a gene pool due to chance;
genetic drift has a much larger effect in a
small population.
• The founder effect occurs when a few
individuals leave the original population and
begin a new population.
• A bottleneck effect is seen when much of a
population is killed due to a natural disaster,
and only a few remaining individuals are left
to begin a new population.
Genetic drift
Founder effect
• Gene Flow
• Gene flow is the movement of alleles
between populations, such as when
individuals migrate from one population to
another.
• Gene flow between two populations keeps
their gene pools similar and prevents close
adaptation to a local environment.
• Nonrandom Mating
• Nonrandom mating occurs when
individuals pair up, not by chance, but
according to genotypes and phenotypes.
• Inbreeding is an example of nonrandom
mating.
• In a human population, inbreeding
increases the frequency of recessive
abnormalities.
• Natural Selection
• Natural selection is the process by which
populations become adapted to their
environment.
• Evolution by natural selection requires:
• Variation
• Inheritance of the genetic difference
• Differential adaptedness
• Differential reproduction.
• Three types of natural selection are
known:
• Stabilizing selection – an intermediate
phenotype is favored.
• Directional selection – one extreme
phenotype is favored.
• Disruptive selection – both extreme
phenotypes are favored over an
intermediate phenotype.
Five-Kingdom System
• The five-kingdom system of classification
is based on structural differences and also
on modes of nutrition among the
eukaryotes.
• The five kingdoms include:
• Monera (prokaryotes)
• Eukaryotic kingdoms of Protista, Fungi,
Plantae, and Animalia.
Five-kingdom system of
classification
Three-Domain System
• The three-domain system recognizes
three domains: Bacteria, Archaea, and
Eukarya.
• This system of classification is based on
biochemical differences that show there
are three vastly different groups of
organisms.
Three-domain system of
classification
The three domains of life
• Chemical evolution likely resulted in the
first cells.
• Inorganic chemicals derived from the
primitive atmosphere reacted to form
simple organic molecules.
• The RNA-first and protein-first hypotheses
seek to explain how the first protocell
arose.
• Eventually, the DNA → RNA → protein
self-replicating system evolved, as did the
first true cell.
• Evolution is a process that involves
changes in gene frequencies in a
population according to Hardy-Weinberg
equilibrium.
• Equilibrium is maintained unless disrupted
by mutations, genetic drift, gene flow,
nonrandom mating, or natural selection.
• Speciation requires geographic isolation
followed by reproductive isolation.
• There are two hypotheses regarding the
pace of evolution – phyletic gradualism
and punctuated equilibrium.
• Classification involves the assignment of
species to a hierarchy of categories:
species, genus, family, order, class,
phylum, kingdom, and domain.
• The three-domain system recognizes
three domains: Bacteria, Archaea, and
Eukarya.