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Principles of Animal Development
Fertilization
Sperm - head with acrosomal cap, midpiece, tail / Live 4-5 days
Egg - surrounded by extracellular matrix called the Zona Pellucida and Follicle Cells called the Corona Radiata
Fertilization
Sperm Cell membrane fuses with egg cell membrane
Egg nucleus and sperm nucleus unite - Zygote
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Stages of Animal Development
Zygote
Early Cleavage Stages
Morula
Blastula
Gastrulation
Gastrula
Neurulation
Organogenisis
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Cleavage - First mitotic divisions in a multicellular Zygote
Cell Divisions without growth in size
Continues until the Morula Stage
-Cleavage Stages
Morula Stage
Solid Balls of Cells
-Blastula Stage
Forms a hollow ball of cells with a fluid cavity (Blastocoel)
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Gastrulation - invagination of cells into the Blastocoel
Form distant cell layers - ”Germ” layers
Pore Created - Blastopore
Cavity is called Archenteron - primitive gut / Inside of our digestive system
Early Gastrula - 2 tissue layers form
Ectoderm - outer layer of cells
Outer Body Tissues
Nervous System skin, teeth, eye and nails
Endoderm - Inner layer of cells
Inner body Tissues
Digestive systems and Glands
Late Gastrula - 3rd Tissue layer form
A middle Mesoderm layer is formed
Middle Body Tissues
Muscular/skeleton system and Cardio/respiratory/reproductive systems
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Neurulation - Formation of the nervous system from the Ectoderm
Neural Folds form moving upward and joining to form a Neural Tube
Becomes the Brain and Spinal Cord
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Organogenesis - Formation of the Organs
Common Traits in Vertebrates
Dorsal Neural Tube
Notochord
Pharyngeal gill pouches / Cause they look like gills
Postanal Tail
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Human Embryonic and Fetal development
Overview
Human Development divided into 2 phases
Embryonic Phase - months 1-2
Fetal Development - months 3-9
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Embryonic development - development of all organ systems
Week 1
Fertilization occurs within the 1/3 of the oviduct
Zygote undergoes the first cleavage divisions as it migrates through the oviduct toward the uterus
After about 3 days it is in the Morula stage
7 days to implantation
Week 2
Implantation occurs
Gastrulation occurs
Week 3
Organogenesis begins
Nervous systems develop
Cardiovascular development begins
Weeks 6-8
Becomes recognizable as human form
All organ systems are now established
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Fetal Development - refinement of these systems
The Fetal period extends from the 3rd through 9th month
The 3rd and 4th months
Ossification of the skeleton begins / Hardening of the Bones
Sex of the individual may be determined
can hear the heartbeat during the 4th month
Enlargement of the Body systems and Fetus occurs until the 9th month (Birth)
Around the 8th month - Fetus sleeps 90-95% of the day, experiences REM Sleep, an indication of Dreaming
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Birth
Contractions occur throughout pregnancy
Stage 1
Cervix begins to dilate
Water Breaks - Amnion ruptured pressure of baby’s head wedged into the Cervix
Stage 1 ends when the Cervix is fully dilated (10cm)
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Stage 2
Contractions are 1-2 minutes apart and last about 1 minute
Urge to Push
Baby “Crowns”
Baby Emerges
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Stage 3
Delivery of the Placenta
Occurs after the Birth of the Baby
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Extraembryonic membranes
In Humans
Chorion develops into the fetal side of the Placenta
Gas and waste product exchange with maternal circulation
Allantois vessels become the umbilical vessels
Amnion contains the amniotic fluid / Has to break to start labor
Yolk Sac is the earliest site of blood cell formation
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What was the thought before Darwin???
Lamarck (1801) - Came up with the idea of Inheritance of Acquired Characteristics
Which Says: The Subconscious ‘desires’ of an organism can cause changes in the traits of that organism
And those changes caused by increased use or disuse will be passed onto the offspring of that individual
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Darwin
Studied medicine and Theology
was the naturalist on a 5 year voyage on the HMS Beagle. 1831
Wrote “The Origin of Species” 1859.
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Darwin and Wallace
While Darwin was researching at his home he received a letter from Alfred Wallace
A young naturalist collecting organisms in South America
This letter was asking advice about an idea Wallace had been working on (Same as Darwin)
So we give Darwin the credit cause he did the most of the work and research (they authored together)
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Evolution
Defined: Genetic change in Organisms over time through reproduction.
Main Points of Evolution
Populations evolve not individuals
Evolution mainly occurs through Natural Selection
Evolution is the main unifying theme of all biology
Example: Pepper Moth
Horse Evolution
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Natural Selection
Variations in form of behavior between members of a species
These variations are inheritable from one generation to the next
There is competition between individuals of a population or species
Those individuals with the adaptable traits will be more likely to reproduce (differential reproduction success) and pass those adaptive traits on with greater frequency to future generations
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Evidence of Evolution
Fossil Record
Artificial selection
Evolution in Action
Comparative Anatomy
Comparative Embryology
BioChemistry and DNA
Biogeography
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Fossil Record
Evidence of past living organisms
What do they tell us?
Past organisms are different from todays living ones
Fossil layers show a trend in evolution from simple to more complex (generally)
Intermediate fossil are being found now.
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Artificial Selection
Shows that change can occur and the environment can cause it
Many examples from our domestication of plants and animals
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Evolution in action
Pesticide resistance in insects
Bacterial and Viral resistance to Medicine
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Comparative Anatomy
comparing the structure of organisms to see if the individuals are related or not
3 Types of Structures
Homologous - Structures that have the same framework (Internal Structure)
Analogous - Structures that dont have the same framework
Vestigial - Structures that have no apparent use in the present owner but are used in related organisms
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Similar Vertebrates Embryos
Genes past through common ancestry
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Biochemistry and DNA
Shows which Organisms are related to each other
How???
DNA and its gene sequence comparison between Humans and Chimps
Red Panda and Giant Panda = Panda is a Bear
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BioGeography
What is it??? Study of life on the planet / Marsupials are in Australia because they are isolated by Geography the placental animals survuved better as the land was notr separated as they better adapted before the split.
Example: large flightless birds descended from a common ancestor, regardless of were they live.
Also deals with Plate Tectonics and Continental Drift. Comes from Geology
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Continental Drift
Idea that the continents were once joined and have since drifted apart. (moves 1-2 inches a year)
Due to plate tectonics
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Plate Tectonics
Earths crust is fractured into plates
Movement of Plates is driven by upwelling of molten Rock at mid-oceanic ridges
As seafloor spreads, older rock is forced down into trenches
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Summary of Darwin’s Theory
Individuals in nature differ from one another
Organisms in nature produce more offspring that can survuve, and many of those who do not reproduce
Because more organisms are produced than can survive, each species must struggle for resources
Each Organism is unique, each has advantages and disadvantages in the struggle for existence
Individuals best suited for the environment survive and reproduce most successful
Species change over time (to survive)
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MicroEvolution
Small scale genetic changes in populations
Causes of Microevolution
Mutation
Gene Flow
Genetic Drift
Natural Selection
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Mutations - Changes ini the DNA that are passed onto the Offspring
(1in a million gametes a mutation occurs)
Types of Mutations
Lethal Mutation
Adaptive Mutation
Neutral Mutation (most common occurring mutation)
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Gene Flow - The exchange of genes between populations
Making populations similar in traits and genetics
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Genetic Drift - The random genetic changes in a population
Sub Types -
Founder Effects -
When a small group of individuals colonize a new habitat and thrive, becoming a new population (Common on Islands)
Bottleneck Effects -
When there is a sever reduction in population size, the resulting population will have less genetic variation and more similar traits (Cheetahs have gone thru 2 Bottleneck effects/They are too similar; sterile)
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Natural Selection -
Types of Natural Selection
Stabilizing Selection
Intermediate forms are favored and extremes are eliminated
Directional Selection
Allele frequencies shift in one direction (Pepper Moth Example)
Disruptive Selection
Allele frequencies shift in two directions!
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Special Population Selection Models
Sexual Selection - When one form or sex chooses its mate based on fitness of that individual. (Chooses the best mate)
Causes a huge amount of genetic change within 1 generation of a population.
Requires Sexual Dimorphism
a species with 2 forms of sex
Occurs only during the mating season
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Genetic (balanced) polymorphism - When there are two forms of a trait that are maintained within a population year after year
Example -
Sickle Cell Trait: Heterozygote Advantage
Sickle Cell is more resistant to Malaria, so it stays around because of the advantage to the population of people who live in Africa (Can only have this through Genetics) Get Malaria from the Female Mosquito only
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Macroevolution
Large Scale genetic change or evolution
Development of new species
What is a species - A group of interbreeding individuals that are reproductively isolated form other such groups (Genetically Distinct) (Cant Breed Together)
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Reproductive isolation
A PreZygotic isolation (Before Sperm and Egg Meet)
Behavioral R.I. - The mating behavior between species keep them from reproducing (King Cobra - mating behaviors - sniff,touch tongues, dance the other and snakes have to rub up against each other to excite to mate 4 ft off the ground)
Ecological R.I. - They live in different habitats
Temporal R.I. - The mating seasons are different
Mechanical R.I. - The reproductive parts don’t fit
Gametic R.I. - The sperm does not survive in the females environment
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PostZygotic Isolation
Zygotic R.I. The embryo dies before birth
Hybrid inviability - The offspring does not survive well and dies before reproductive age
Hybrid Sterility - The offspring is sterile and can’t pass on the new genetics (Like a Mule - Female Horse and a Male Donkey can only produce this)
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Hybrids (Horse and Zebra)
Zorses! (It can produce on its own / New Species) Wacky things happen on Farms changes the mating rituals of each species
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Speciation & Natural Selection
Natural Selection can lead to speciation
Speciation - can also occur as a result of other microevolutionary processes
Genetic Drift
Mutation
Etc...
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Speciation Models
Allopatric Speciation - The development of new species by a physical separation from the original species (Oceans, Mountains, etc.)
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Sympatric Speciation - The development of a new species within the same environment as the original species
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Rates of Speciation
Gradualism - at a slow and gradual rate
Punctuated Equilibrium - The development of new species in a short amount of time, then those species remain the same
(SubType - Adaptive Radiation) - is the new development of ALOT of new species at one time. (Has happened 7 times on the planet, always after 85% extinction of organisms)
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Extinctions
3 types
Local Extinctions - a part of species in a specific area
Species Extinction - Entire Species is Gone forever (Cheetahs are next for Example)
Mass Extinctions
have played a major role in evolutionary history (Are in the middle of the 7th now) The 6th one was the (Ice Age)
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