What triggers the formation of the fertilization membrane in sea urchins?
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The action of a cortical granule enzyme that causes the vitelline envelope to harden.
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What triggers the formation of the fertilization membrane in sea urchins?
The action of a cortical granule enzyme that causes the vitelline envelope to harden.
What role do Hox genes play in gene expression?
They are master genes that control the expression of subordinate genes.
What can changes during development create within a species?
Diverse variation that natural selection can act on.
What role do Hox genes play in gene expression?
They are master genes that control the expression of subordinate genes.
Are Hox genes homologous in diverse organisms?
Yes, they are homologous across different species.
What will the second opening become in protostome development?
The anus.
What occurs on the egg surface after the first sperm enters?
Numerous changes block the entrance to any additional sperm.
What is the function of the fertilization membrane?
Acts as a permanent physical barrier to prevent polyspermy.
How are Hox genes characterized across different organisms?
They are homologous in diverse organisms.
What do Hox genes control in embryos?
The subdivision into regions of different developmental fates along the anteroposterior axis.
In protostome development, what does the blastopore become?
The mouth.
What is significant about Isla Daphne Major?
It is a notable location for studies in evolution and ecology.
Why are marine invertebrates like sea urchins and fishes preferred for fertilization studies?
They release large amounts of eggs and sperm that are easy to keep and study in the laboratory.
When were Hox genes discovered?
In the 1970s and 1980s.
What is direct development?
When lots of nourishing yolk is present, embryos develop into a miniature adult.
What is the current concept of development primarily based on?
Epigenetic concepts.
What type of coelom development do vertebrates use?
A modified version of schizocoely.
What occurs after embryonic cell division creates different cells?
The cells begin to influence each other's fates by induction.
What factors are the two medium ground finches compared on?
Same species, same island, same age, same sex.
What does polyspermy refer to?
The fertilization of an egg by multiple sperm.
What is UBX/Hoxc-8?
A highly conserved transcription factor found in both invertebrates and vertebrates.
What does the term 'protostome' mean?
First mouth.
What is the fertilization cone?
It forms where the sperm contacts the vitelline membrane.
What role do changes in development play in evolution?
They create diverse variations that natural selection can act on.
How does natural variation within a species contribute to natural selection?
Natural variation provides the traits on which natural selection can act.
What is the difference between variation within a species and variation between species?
Variation within a species refers to differences among individuals of the same species, while variation between species refers to differences among distinct species.
What role do Hox genes play in development?
Hox genes control development and are similar across diverse groups of animals.
What forms a diploid zygote nucleus?
The fusion of male and female pronuclei.
What species is used as an example to illustrate variation in bill sizes?
Medium ground finches (Geospiza fortis).
How is position-specific expression achieved in early embryonic development?
Through segmentation genes that establish spatial patterns of transcription factors.
What is ectopic expression?
Expression of a gene in a location where it is not normally expressed.
How do most marine invertebrates and fishes fertilize their eggs?
By releasing enormous numbers of sperm into the ocean.
Why is species-specific recognition important in marine environments?
Many closely related species may be spawning at the same time.
What two cavities are formed during development following cleavage?
Gut cavity (gastrointestinal tract) and fluid-filled coelom (body space).
What does the mesoderm around the coelom produce?
Layers of muscles and internal body parts.
What happens during the slow block reaction?
Fusion of cortical granules with the egg membrane, releasing contents that create an osmotic gradient.
What is indirect development?
When little yolk is present, young develop into larval stages that can feed.
What is the enlarged sperm nucleus called?
The male pronucleus.
What are blastomeres?
Small, maneuverable cells formed from the large cytoplasmic mass during cleavage.
What are the two genes that influence the bill shape of Galapagos finches?
BMP4 and CaM.
Who is associated with the concept of variation between species?
Ernst Haeckel.
What are major questions in evolutionary developmental biology?
The genetic basis of developmental instructions and the role of developmental evolution in the history of life.
What is totipotency?
The ability of a zygote to develop into all cell types found in the adult.
What is ecdysis?
The shedding of the cuticle.
What type of eggs have very little yolk distributed evenly in the cytoplasm?
Isolecithal eggs.
What type of seeds do small-beaked birds typically feed on?
Smaller seeds.
What is the significance of inductive signals in vertebrate limb formation?
Inductive signals play a major role in pattern formation, which is the development of an animal's spatial organization.
What is the difference between variation within a species and variation between species?
Variation within a species is derived from genetic differences among individuals, while variation between species involves distinct genetic traits that separate species.
What usually involves changes in the shape of a cell?
Reorganization of the cytoskeleton.
What is the first step when sea urchin sperm finds an egg?
It has to penetrate a jelly layer around the egg.
What is the role of Hox genes in development?
Differences in Hox gene expression patterns result in major differences in body plans.
What prevents additional sperm from binding to the egg in mammals?
The cortical reaction releases enzymes that modify the egg surface.
What effect do cytoplasmic determinants have on blastomeres?
They set up differences in blastomeres resulting from cleavage.
What can result from Natural Selection acting on variation within a population?
Speciation.
What mechanism is responsible for variation or diversity between species?
Natural selection.
How does evolution affect organisms?
Organisms become different as a result of changes in the genetic control of development.
How do mammals nourish their embryos despite having little yolk?
Through the placenta.
What occurs in the zygote after the fusion of pronuclei?
Several cytoplasmic changes to prepare for cleavage.
On what does natural selection act?
Populations.
What are the key components of building a body plan?
Cell movement, changes in adhesion, and cell proliferation.
Where can you find more information about the genetic evolution of Darwin's finches?
At the Nature website, specifically the article on the evolution of Darwin's finches.
What do Hox genes regulate?
The transcription of other genes involved in development.
How many germ layers do diploblastic organisms have?
Two germ layers.
What type of cleavage occurs in isolecithal eggs?
Holoblastic cleavage.
What does positional information tell a cell?
Where it is with respect to the animal's body axes.
What is Pax6/eyeless associated with?
It is a highly conserved transcription factor important for eye development.
What are morphogenetic determinants?
Components that influence the development of specific cell fates.
What role do egg-recognition proteins play in fertilization?
They bind to species-specific sperm receptors on the vitelline envelope to ensure recognition of the same species.
What are the three germ layers formed after cleavage?
Ectoderm (outer layer), Mesoderm (middle layer), Endoderm (inner layer).
What is the big question regarding diversity in species?
How do we get diversity between species versus variation within a species?
What are homeotic selector genes responsible for?
Controlling the patterning of body structures.
What does gastrulation in a sea urchin produce?
An embryo with a primitive gut (archenteron) and three germ layers.
What occurs as a result of developmental decisions?
Cellular diversity.
Does cell growth occur during cleavage?
No, only subdivision occurs until cells reach regular somatic cell size.
What is an example of species that can show variation?
Different species of bats.
How is development organized?
As a sequence of local patterns where one step is a subunit of another, with each step being a necessary preliminary for the next.
What occurs during the cortical reaction in mammals?
Enzymes are released that modify the egg surface to prevent any sperm from binding.
What forms at the site where the sperm contacts the egg's vitelline membrane?
A fertilization cone.
What happens to the sperm head during fertilization?
It is drawn in and fuses with the egg plasma membrane.
What are MADS-box genes?
A similar group of genes in plants that influence plant development.
What is the significance of Hox genes?
They are essential metazoan genes that determine the identity of embryonic regions along the anterior-posterior axis.
What is induction in developmental biology?
The capacity of some cells to evoke a developmental response like shape and fate in other cells.
How can induction be influenced?
Induction can be influenced reciprocally.
What leads to the development of diverse cell types in the animal body?
Conditions created in preceding stages.
How are novel phenotypes introduced into a population?
Through developmental processes.
What are the three tissue layers produced by gastrulation called?
Embryonic germ layers.
What does the ectoderm form?
The outer layer of the gastrula, including outer surfaces and neural tissue.
What is a complete gut?
A pathway from the mouth to the anus.
What do Hox genes control in embryonic development?
The subdivision of embryos into regions of different developmental fates along the anteroposterior axis.
Why is there variability in bill sizes within the same species?
Due to changes during development.
What role do transcription factors play in the expression of HOX genes?
They drive the spatial pattern of HOX gene expression.
What do HOX genes trigger in developmental pathways?
Cascades of developmental gene pathways via transcription factors.
What challenge do small sperm face in the ocean?
Fertilization is difficult due to the vastness of the ocean.
What do many eggs release to attract sperm?
A chemotactic molecule to attract sperm of the same species.
What is a universal property of animals regarding fertilization?
Species-specific recognition proteins.
What happens to the sperm head during fertilization?
The sperm head is drawn in and fuses with the egg plasma membrane.
What does the induction of legs or eyes by a mutation in one gene suggest?
It suggests that these and other organs can develop as modules.
What role do cytoplasmic determinants play in the egg cell?
They are important in establishing the body axes.
What is the primary focus of research on fertilization and activation?
Much of the knowledge is based on marine invertebrates, especially sea urchins and fishes.
What is the primary mechanism that leads to diversity within species?
Natural Selection acting on variation within a population.
What is evolutionary developmental biology (Evo-Devo)?
It is the study of how evolution leads to differences in organisms due to changes in genetic control of development.
What does the male pronucleus do after formation?
It migrates inward to contact the female pronucleus.
What is the result of the osmotic gradient created during the slow block?
Water rushes into the space, elevating the envelope and lifting away all bound sperm except the one that fused with the egg.
What is formed as a result of the slow block reaction?
The fertilization membrane.
Where is segment-specific expression observed in mice?
In the hindbrain.
What initiates the process of development?
The mitotic division of a fertilized egg to produce a multi-celled embryo.
What is a mechanism for evolution that explains variation between species?
Natural Selection.
What is morphogenesis?
The process by which an animal takes shape and differentiated cells end up in their appropriate locations.
What type of cleavage is characteristic of protostomes?
Spiral cleavage.
How do BMP4 and CaM affect bill shape?
They influence the size and shape of the bills.
What process rearranges the cells of a blastula into a three-layered embryo?
Gastrulation.
What is the pattern of HOX gene expression?
Highly conserved anterior-posterior patterns.
What can happen to a blastomere isolated early in cleavage in Deuterostomes?
It can form a whole individual.
How do large-beaked birds benefit in their feeding habits?
They can crack big, hard seeds.
What is the 'fast block' in sea urchin fertilization?
An electrical potential change that rapidly spreads across the membrane to prevent the entry of other sperm.
How does natural variation within a species lead to natural selection?
Natural variation provides the raw material on which natural selection can act, favoring traits that enhance survival and reproduction.
What type of development is characterized by cell fate being determined by cytoplasmic components in each blastomere?
Mosaic development.
Where is Isla Daphne Major located?
In the Galápagos Islands.
What is an example of how Hox genes can influence development in arthropods?
Hox gene changes can alter the number of legs.
What is the slow block in sea urchin fertilization?
A cortical reaction that occurs after the fast block event.
What is formed when the sperm nucleus enlarges?
The male pronucleus.
How does the expression of Hox genes occur?
In an anterior-posterior pattern.
What does development represent in an individual?
A series of progressive changes from beginning to maturity.
What is the blastopore?
The open end of the gut that becomes the anus in deuterostomes.
What is induction in the context of embryonic development?
Induction is the capacity of some cells to cause other cells to develop in a certain way.
What role does the dorsal lip of the blastopore play in development?
It induces neural development.
What are the two clades of protostomes mentioned?
Ecdysozoan protostomes and other taxa that molt their exoskeletons.
What is the Homeobox?
A highly conserved amino acid coding sequence shared among Hox genes that binds DNA.
What role do Hox genes play in development?
They regulate the transcription of other genes involved in gene cascades during development.
What are the molecular cues that control pattern formation in vertebrate limb development called?
Positional information.
What determines bill shape within the same species?
Specific genes.
In which organisms are isolecithal eggs found?
Echinoderms, tunicates, cephalochordates, molluscs, and mammals.
How do switches affect gene expression during development?
They turn genes on and off during different phases of development.
What is a mechanism for evolution?
Natural selection.
What role does cell migration play in gastrulation?
It causes tissue invagination through changes in cell shape and migration.
What are the two basic processes responsible for progressive subdivision of cells?
Cytoplasmic specification and induction.
What are actins and tubulins used for in the zygote?
They are needed for cell division.
What is the sequence of mitotic divisions called that the zygote undergoes?
Cleavage.
What is a coelom?
A coelom is a body cavity surrounded by mesoderm.
What activates the egg to begin development?
Fertilization.
What happens to the original cytoplasm during cleavage?
It is continuously divided into smaller units.
Where is the blastocoel located in frogs?
In the animal hemisphere.
How is the second opening of the gut formed?
By merging of the archenteron tube with the ectoderm.
What is the characteristic of meroblastic cleavage?
Incomplete division of the egg.
What happens in a mouse lacking Pax6?
It results in developmental defects, particularly in eye formation.
Can an isolated blastomere develop on its own?
No, it cannot develop.
What is a key concept in Evolutionary Developmental Biology (Evo-Devo)?
Evolution could proceed by relatively few mutations in a few developmental genes instead of gradual accumulation of numerous small mutations.
From which layers do all other structures derive?
From one of the three germ layers.
Which vertebrates have been studied for fertilization?
Mice, rabbits, and hamsters.
What is formed when the male and female pronuclei fuse?
A diploid zygote nucleus.
What is cell differentiation?
The specialization of cells in their structure and function.
What are cytoplasmic determinants?
Substances unevenly distributed in the egg that lead to differences in cell fate.
What happens to the original cytoplasm during cleavage?
It is continuously divided into smaller units.
How is the fertilization membrane formed?
It is formed when one cortical granule enzyme causes the vitelline envelope to harden.
Do mammals have a fertilization membrane?
No, mammals do not have a fertilization membrane.
What type of cleavage do telolecithal eggs undergo?
Meroblastic or incomplete cleavage.
What type of embryo is formed in triploblastic organisms?
A three-layered embryo.
What significant event is referred to as 'The BIG Drought'?
The drought that occurred from 1976 to 1977.
In which organisms are telolecithal eggs commonly found?
Birds, reptiles, most fishes, and a few amphibians.
What effect did the dorsal blastopore lip have on the host ectoderm?
It induced the host ectoderm to form a neural tube.
How does morphogenesis differ between plants and animals?
In animals, it involves the movement of cells, while in plants it does not.
What is the significance of bill size in G. fortis?
It is a trait that influenced survival during drought conditions.
Where is the yolk concentrated in mesolecithal eggs?
In the vegetal pole.
How do eggs cleave in the yolk-rich vegetal pole of mesolecithal eggs?
Slowly and following a radial direction.
What is enterocoely?
The process where the coelom forms as outpocketing of the gut.
What are pseudocoelomates?
Organisms with a body cavity between mesoderm and endoderm.
What are acoelomates?
Organisms with no body cavity other than the gut.
What process converts the blastula into a 2 to 3 layer embryo?
Gastrulation.
What is a trochophore larva?
A larval form that features all four protostome characteristics.
When does sperm typically enter the primary oocyte in many organisms?
Before meiosis is completed.
What type of cleavage occurs in birds?
Meroblastic cleavage.
In some species, what role does sperm play in egg activation?
Sperm is required for egg activation but contributes no genetic material.
Which structures affect the formation of the neural tube?
Microtubules and microfilaments.
What is the vitelline envelope?
A thin membrane above the egg plasma membrane.
What happens to the sperm nuclear envelope during fertilization?
It breaks apart to allow chromatin to expand.
What do Hox genes control in animals?
The morphology of segments.
Which example is often used to illustrate variation within a species?
Galapagos Finches.
How do typical deuterostomes develop their coeloms?
By enterocoely.
What organisms are included in the group of Deuterostomes?
Echinoderms (like sea urchins and sea stars) and chordates.
What is the significance of the fusion of sperm and egg nuclei?
It forms a diploid zygote nucleus, which is crucial for development.
What does evolutionary developmental biology link together?
Genetics with evolution through the agencies of development.
What role does the position of cells in the early embryo play?
It results in differences in cell fate.
What is the three-layered embryo formed during gastrulation called?
Gastrula.
In many species, which stage is typically totipotent?
The zygote.
Can changes during development create diverse variation within a species?
Yes, these changes can provide the variation that natural selection acts upon.
What is the big question in the context of natural selection?
How do we get phenotypic variation?
How do different genes affect embryonic development?
Different genes will be expressed in different cells.
What was the observed increase in bill size among survivors of G. fortis in 1976?
4% increase.
What do the wings and legs of chicks begin as?
Bumps of tissue called limb buds.
What are the two major groups of triploblastic animals?
Protostomes and Deuterostomes.
How do inducers work in the process of induction?
Inducers work with surface proteins of adjacent cells or by diffusion of growth and differentiating molecules.
What happens as interactions between cells become increasingly restrictive?
Each new stage limits developmental fate.
How might natural selection act on novel phenotypes?
By favoring traits that enhance survival and reproduction.
What is the mesoderm and how does it form?
The mesoderm is the third germ layer that forms between the endoderm and ectoderm, and it forms through the proliferation of cells near the blastopore or by pushing the archenteron wall into the space between the archenteron and the outer body wall.
What characterizes the animal pole of the embryo?
It contains mostly cytoplasm.
What does inheritance refer to in the context of natural selection?
Individuals pass on at least some of their traits to their offspring.
What is the animal pole?
The pole of the egg with the least yolk.
What occurs during meiosis in oocytes?
Two chromosomal divisions occur, forming four haploid nuclei.
What factors can affect cleavage?
Quantity and distribution of yolk, and genes controlling symmetry.
When do most preparations in the egg occur in mammals?
During the prolonged prophase I.
What are the four types of yolk distribution in animal eggs?
Isolecithal, Mesolecithal, Telolecithal, Centrolecithal.
What must individuals within a population do for natural selection to occur?
Individuals must vary phenotypically.
How does cellular potency change during embryonic development?
The potency of cells becomes progressively more limited.
What is the process of maturation for the primary oocyte?
It involves specific developmental stages leading to oocyte readiness for fertilization.
What happens to the sperm after the membranes of sperm and egg fuse?
The sperm loses its flagellum and its nuclear envelope breaks apart.
What occurs in the zygote to prepare for cleavage?
Several cytoplasmic changes.
What did Thomas Huxley advise Darwin in 1857 regarding differences between organisms?
That differences result not so much from the development of new parts but from the modification of existing parts common to divergent types.
What is the function of the fertilization membrane?
It acts as a permanent physical barrier to prevent polyspermy by hardening the vitelline envelope.
Is there a master control panel directing development?
No, there is no 'hard-wired' master control panel directing development.
What is referred to as the primary organizer in embryonic development?
The dorsal lip of the blastopore.
What limitation do small-beaked birds face?
They cannot crack large, hard seeds.
What species is being studied for rapid evolution of bill size?
Medium ground finches (Geospiza fortis).
What is a transcription factor?
A protein that affects the transcription of an associated gene by interacting with a regulatory DNA sequence.
What mechanism does the sea urchin use to prevent polyspermy?
A 'fast block' occurs, which is an electrical potential change that spreads across the membrane.
What changes occur on the egg surface after the first sperm enters?
Numerous changes block the entrance of any additional sperm.
What was the bill size of G. fortis offspring born in 1976?
Average bill size was 11.3 mm.
What does the data suggest about the survival of G. fortis during the drought?
There was differential survival based on bill size.
What type of cleavage do mesolecithal eggs undergo?
Holoblastic (complete cleavage).
How does the cleavage furrow behave in mesolecithal eggs?
It extends completely through the egg.
What is superficial cleavage?
Cleavage that restricts division to the cytoplasmic rim of the egg.
In which organisms does centrolecithal egg cleavage occur?
In arthropods like insects.
What is the role of the endoderm?
It lines the embryonic digestive tract.
What are the two types of coelomic cavity formation?
Schizocoely, which forms by splitting mesoderm, and enterocoely, which forms by out-pocketing of mesoderm from the endoderm.
What do the ectoderm and endoderm layers form?
The endodermal tube or the gut.
What factors contribute to the size difference in the bills of Geospiza fortis?
How much and when genes are turned off and on.
What are morphogenetic determinants responsible for during post-fertilization development?
They direct the activation and repression of specific genes.
In which species does meroblastic cleavage occur?
Species with yolk-rich eggs, such as reptiles and birds.
What defines mesolecithal eggs?
A moderate amount of yolk concentrated at the vegetal pole.
What does the slope of the bill size graph (1976=1978) indicate?
It indicates a heritable trait with a slope of approximately 0.7.
What happens during cleavage in the embryo?
The embryo divides repeatedly, with both nuclei and cytoplasm dividing completely.
Which organisms are included in protostomes?
Flatworms, annelids, and molluscs.
What type of cleavage is characteristic of Deuterostomes?
Radial cleavage.
What is natural selection?
A mechanism for evolution that acts on phenotypic variation.
What does Evo-Devo study?
The development processes in organisms to understand evolutionary relationships and the emergence of novel phenotypes.
Why is phenotypic variation important for natural selection?
Natural selection can only act on populations that exhibit phenotypic variation.
What are the two main focuses of Evo-Devo?
What determines an organism's development?
The genome of the zygote and differences that arise between early embryonic cells.
What is a characteristic of cleavage in telolecithal eggs?
Cleavage furrow does not cut through the heavy yolk.
How does positional information affect a cell's descendants?
It determines how they respond to future molecular signals.
What complicates gastrulation in frogs?
Yolk-laden cells in the vegetal hemisphere and a blastula wall that is more than one cell thick.
What are the two key components required for induction?
Inducer and responder.
What type of yolk disposition do mesolecithal eggs have?
Moderate vegetal yolk disposition.
What type of cleavage occurs in centrolecithal eggs?
Meroblastic cleavage.
What is the initial event in sexual reproduction?
Fertilization, the union of male and female gametes.
What is located at the vegetal pole of the embryo?
Yolk.
What is the second condition for natural selection?
Individuals within a population must vary phenotypically.
What does the mesoderm partly fill?
The space between the endoderm and ectoderm, forming muscles and the reproductive system.
What do lophotrochozoan protostomes include?
Annelid worms, molluscs, and some small phyla.
How do animal pole blastomeres compare in size to vegetal pole blastomeres in frogs?
Animal pole blastomeres are smaller.
How many openings does the endodermal tube have?
Two openings.
In some taxa, when does sperm enter the oocyte?
After the first or second meiotic divisions.
What is artificial parthenogenesis?
The process where eggs are artificially induced to initiate development without sperm.
What characterizes isolecithal eggs?
Very little yolk with even distribution.
What is a blastula?
A hollow ball of cells with a fluid-filled cavity called the blastocoel.
What is meant by regulative development in Deuterostomes?
The fate of a cell depends on its interactions with neighbors, not on the cytoplasm it contains.
What is the primary factor influencing bill size in medium ground finches?
Natural selection based on seed size.
What is the primary question regarding species variation?
How do we get this variation or diversity between species?
What is polyspermy?
The entry of more than one sperm to one egg, which is harmful to normal development.
Where is the yolk concentrated in telolecithal eggs?
At the vegetal pole.
Why are homeotic genes important?
They produce complementary effects necessary for the ordered development of an organism.
What did the transplanted dorsal blastopore lip develop into?
A notochord and somites.
What is conditional specification in development?
The fate of a cell is not fixed until it receives positional information from neighboring cells.
In which organism was the Spemann-Mangold experiment conducted?
Salamander.
What drives cell migration?
The cytoskeleton.
What type of eggs are characterized by having much yolk concentrated in the center?
Centrolecithal eggs.
Does the cleavage furrow cut through the yolk in centrolecithal eggs?
No, it does not cut through the yolk at all.
In which type of organisms do mesolecithal eggs occur?
Amphibians.
Which animals retain a blind gut?
Some invertebrates like sea anemones.
What is the size difference between the egg and sperm?
The egg is normally 200 times larger than somatic cells, while sperm is only 1/50 the size.
What is the cleavage pattern in frogs relative to?
The animal and vegetal poles of the zygote.
What is a morula?
A solid ball of cells formed after the first 5-7 divisions.
What components are found in the cytoplasm of the egg during oogenesis?
mRNA, ribosomes, tRNA, and other elements for protein synthesis.
How does the polarity of the egg influence body axis development in frogs?
It determines the anterior-posterior axis before fertilization.
What happens during the first cleavage division in frog embryos?
It bisects the gray crescent.
How do different traits affect survival or reproductive success?
Individuals with different traits differ in their survival or reproductive success during the struggle for existence.
What distinguishes centrolecithal eggs?
Lots of yolk that is centrally located.
What is a primitive gut?
The structure present in a gastrula formed during gastrulation.
Do many ecdysozoans show spiral cleavage?
No, many do not show spiral cleavage.
What is the difference between variation within a species and variation between species?
Variation within a species refers to differences among individuals of the same species, while variation between species refers to differences among distinct species.
How does the cleavage furrow behave in isolecithal eggs?
It extends completely through the egg.
What was the rainfall measurement in millimeters during the years 1976 and 1977?
The data indicates a significant drop in rainfall during these years, leading to drought conditions.
What is morphogenesis?
A major aspect of development involving the movement of cells, primarily in animals.
What was the bill size of G. fortis offspring born in 1978 compared to 1976?
4% increase in offspring bill size from 1976 to 1978.
How might we observe changes in frequencies of bill sizes?
Through the action of natural selection over time.
What is evolutionary development (Evo-Devo)?
A field that studies how evolutionary processes influence development.
What forms before the coelom in protostome development?
A mesodermal band of tissue.
What is the process called when the mesoderm splits to form a coelom?
Schizocoely.
What does fertilization restore in the nucleus?
The diploid number of chromosomes.
What is the vegetal pole?
The pole of the egg with the most yolk.
How is a complete gut formed?
Through the inward movement of the archenteron until it reaches the ectodermal wall of the gastrula.
What happens to an egg during oogenesis?
It grows in size by accumulating yolk.
What is the opening into the second cavity called during gastrulation?
Blastopore.
What is necessary for individuals to form the next generation?
Individuals must reproduce.
What happens after meiosis resumes in oocyte maturation?
The egg is ready to fuse its nucleus with the sperm nucleus.
What is the blastoderm in birds?
A cap of cells on top of the yolk.
How does bill size relate to heritability?
Small-billed parents breed small-billed offspring, and large-billed parents breed large-billed offspring.
What is the role of homeotic proteins?
They can activate one gene while repressing another, ensuring ordered development.
What is a homeobox?
A sequence of DNA within homeotic genes that encodes a segment of 60 amino acids.
What was the main focus of the Spemann-Mangold experiment?
Transplanting a piece of dorsal blastopore lip from a salamander gastrula.
What are the possible directions of division in isolecithal eggs?
Radial, spiral, or rotational.
What factors influence the shape of a bill?
How much each gene is expressed and when each gene is expressed.
What do embryonic cells within a limb bud respond to?
Positional information indicating location along three axes.
What are the two types of coelom formation in triploblastic animals?
Schizocoelous and enterocoelous coelom formation.
What happens to the blastopore in deuterostome development?
It becomes the anus, and the mouth develops as the second opening.
What processes are initiated after the removal of metabolic inhibitors?
A burst of DNA and protein synthesis occurs using mRNA stored in the egg cytoplasm.
What is a blind or incomplete gut?
When the embryonic gut opens only into the blastopore.
What distinguishes diploblastic animals from triploblastic animals?
Diploblastic animals have two germ layers, while triploblastic animals have three germ layers.
What is cleavage in embryonic development?
A series of rapid cell divisions following fertilization.
How do individuals with different traits affect natural selection?
They differ in their survival or reproductive success.
What is the size difference between the two medium ground finches (Geospiza fortis)?
One bill is 25% bigger than the other.
What happens to the nuclei formed during oocyte meiosis?
One nucleus stays within the oocyte while three move outside to form three polar bodies.
What layers does the gastrula consist of?
An outer layer of ectoderm and an inner layer of endoderm.
Is sperm always required for development?
No, some species can initiate development without sperm through artificial parthenogenesis.
What is natural parthenogenesis?
A phenomenon where some species have eggs that develop normally in the absence of sperm.
What is the characteristic of telolecithal eggs?
Lots of yolk at the vegetal pole.
What is the apical ectodermal ridge (AER)?
A thickened area of ectoderm at the tip of the limb bud.
What is the result of gastrulation in frogs?
An embryo with a gut and three germ layers.
What is the function of the Homeobox DNA sequence?
It is involved in the regulation of patterns of anatomical development.
How are protostomes and deuterostomes differentiated?
By spiral vs. radial cleavage, regulative vs. mosaic cleavage, and whether the blastopore becomes the mouth or anus.
What does the term 'Deuterostome' mean?
Second mouth.
What is a coelom?
A body cavity completely surrounded by mesoderm.
What establishes polarity in the embryo before cleavage begins?
The animal-vegetal axis.
What is the first condition for natural selection?
Individuals must reproduce to form the next generation and produce more than what will survive.
What defines the polarity of eggs and zygotes in many animals?
The distribution of yolk.
What are blastomeres?
Small maneuverable cells formed during cleavage.
What is a blastomere?
Each cell formed during cleavage.
What is formed during gastrulation that creates a new internal cavity?
The archenteron or gastrocoel.
What is the germinal vesicle?
The egg nucleus that grows in size, bloated with RNA.
What do the resources in a mature oocyte support?
The nutritional requirements of the embryo after fertilization and direct its development through cleavage.
What is the function of the zone of polarizing activity (ZPA)?
It organizes limb development and is located underneath the ectoderm at the posterior side of the bud.
What direction does cleavage follow in telolecithal eggs?
Discoidal direction.
What role does natural selection play in bill size variation?
Natural selection acts on the different bill sizes, influencing their frequencies.
What is cell migration?
The active movement of cells from one place to another.
What happens to the egg after fertilization?
Inhibitors of metabolism are removed, allowing the egg to initiate metabolism.
How do mesoderm and coelom form in deuterostomes?
They form simultaneously.
What does fertilization provide for?
Recombination of paternal and maternal genes.
What occurs during cleavage in terms of cell division?
Both nuclei and cytoplasm divide completely, leading to multicellular formation.
What happens to the blastopore in some organisms?
It becomes the mouth in some creatures and the anus in others.
Does cell growth occur during cleavage?
No, only subdivision occurs until cells reach regular somatic cell size.
What surrounds the gut in the gastrula?
The blastocoel.
What occurs during cleavage in terms of growth?
Very little growth occurs.
What is the gray crescent in frog development?
A region of lighter-colored cytoplasm that marks the dorsal side.
What percentage of resemblance in bill size between parents and offspring is due to heritable factors?
60 - 75%.
What advantage do large-billed birds have?
They survive and reproduce better when large seeds prevail.
How are schizocoely and enterocoely functionally related?
Both types of coelomic cavities are functionally equivalent.
What is a lophophore?
A horseshoe-shaped feeding structure.
What is the significance of coelom formation in evolutionary biology?
Coelom formation is an inherited character and can be used as evidence of shared ancestry.
What type of cleavage occurs in frogs?
Holoblastic cleavage.
What is the concept of inheritance in relation to traits?
Individuals pass on at least some of their traits to their offspring.
What characterizes a mature oocyte?
It has become a highly structured system with abundant resources.
What advantage do small-billed birds have?
They are more efficient and leave more offspring when small seeds are relatively common.
