Biology Quiz on Eumetozoa and Embryonic Development

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Questions and Answers

What is a characteristic of the Eumetozoa group?

Contains tissue organized into 2 or 3 germ layers (correct)

Has no neurons present

Includes sponges and placozoa

Does not go through a gastrula stage

What stage does a human embryo reach after the zygote phase?

Blastocyst

Gastrula

Blastula (correct)

Germ layer

What is the function of Hox genes in segmented animals?

To determine the body plan and symmetry

To control the development of specific organs

To regulate the number of embryonic germ layers

To confer identity to each segment along a head to tail axis (correct)

Which of the following statements about the Cnidaria phylum is true?

It is radially symmetric even as embryos. Signup and view all the answers

How does the gastrula in eumetazoans differ from the blastula stage?

The gastrula has more tissue layers. Signup and view all the answers

What is a major evolutionary feature of the ground plan in each phylum?

It is often modified by natural selection. Signup and view all the answers

Which group of animals is characterized by a chitinous exoskeleton and segmented body?

Phylum Arthropoda Signup and view all the answers

What distinguishes the embryonic development of sponges from eumetazoans?

Sponges form a blastula without invagination. Signup and view all the answers

Which statement about Deuterostomes is correct?

Deuterostomes have significant developmental differences compared to protostomes. Signup and view all the answers

What is a key characteristic of Phylum Chordata?

Development of a dorsal hollow nerve cord. Signup and view all the answers

Which of the following features is characteristic of Arthropods?

Ventral nerve cord. Signup and view all the answers

How is the respiratory system in Insecta primarily described?

Employs tracheae as respiratory structures. Signup and view all the answers

Which statement about the notochord in Chordates is accurate?

In most vertebrates, it is replaced by a jointed skeleton. Signup and view all the answers

Which group of animals falls under the major phylum Echinodermata?

Starfish. Signup and view all the answers

What is tagmosis in relation to arthropod evolution?

The specialization and fusion of segments. Signup and view all the answers

Which feature do Crustacea typically possess?

Biramous appendages. Signup and view all the answers

What is a primary characteristic of the amniotic egg that allows amniotes to thrive in arid environments?

It contains specialized membranes for exchange and storage. Signup and view all the answers

Which group of amniotes includes mammals and their descendants?

Synapsids Signup and view all the answers

What adaptation is essential for embryonic development in amniotes with high yolk content?

Development of embryonic membranes that grow over the embryo. Signup and view all the answers

Which type of skin adaptation helps reptiles prevent water loss?

Scales made of keratin. Signup and view all the answers

How do all surviving reptiles primarily regulate their body temperature?

Using behavioral patterns and external heat sources. Signup and view all the answers

Which of the following is NOT a characteristic feature of an amniotic egg?

External fertilization onset. Signup and view all the answers

What type of cleavage occurs in the embryonic development of amniotes?

Discoidal cleavage that does not penetrate the yolk. Signup and view all the answers

What describes the paraphyletic nature of the term 'reptiles'?

It excludes some descendants of a common ancestor. Signup and view all the answers

Study Notes

Eumetozoa

This group encompasses all animal life excluding sponges and placozoa.
Tissues are organized into two or three germ layers.
Neurons are present.
Embryos undergo a gastrula stage.
Originated in the Ediacaran period. Dickinsonia might have been an early example.

Embryological Development

All animals begin as a zygote.
The zygote rapidly divides into a ball of cells.
This ball of cells organizes into a blastula, a hollow structure with an internal blastocoel.
Sponges develop directly from the blastula stage.
In eumetozoa, blastulas invaginate to form a gastrula.
The gastrula has a blastopore and two layers of cells.
The interior archenteron gives rise to the gut, and the blastocoel is sandwiched between the layers, with the blastopore potentially serving as a mouth or anus.

Hox Genes

Hox genes are related homeotic genes common to most animals (with the exception of sponges and ctenophores).
In animals with segmented bodies, Hox genes determine the identity of each segment along the head-to-tail axis.
Hox genes act as transcription factors, and contain a homeobox DNA sequence.
The arrangement of Hox genes on chromosomes mirrors their location on the anterior-posterior axis in many animals.
Similar Hox genes suggest a common ancestor for all bilaterians.
The evolution of Hox genes may have paved the way for the evolution of complex body forms.

Ground Plan

Each phylum possesses a ground plan deeply rooted in developmental biology, defining the overall body structure, including cavities and organ systems.
Ground plans are relatively conserved throughout evolution; however, they've been modified numerous times in various organisms, making the original layout sometimes hard to discern.
Examine your own body plan for key features of the chordate body plan.
Example - Phylum Arthropoda (segmented body, chitinous exoskeleton, periodic molts, and jointed appendages).

Cnidaria

Cnidarians display radial symmetry, even in their embryos.
The body is composed of only two tissue layers surrounding a jelly-like inner layer.
Includes jellyfish, anemones, hydras, gorgonians, and corals. There are over 10,000 species, all exclusively aquatic.
Cnidarian bodies consist of a jelly-like non-living mesoglea sandwiched between two layers of epithelium, one cell thick.
An internal body cavity serves as a digestive tract and for respiration.
They have a nerve net, and are radially symmetrical. Many groups alternate between polyp and medusa forms. They have specialized cells (cnidocytes) that entangle or harpoon prey.

Bilateria

These include eumetozoa other than radiates.
Bilaterians have three tissue layers (ectoderm, endoderm, mesoderm - triploblastic).
Protostomes develop the mouth first, spiral cleavage, determinate development, and coelom forms from splitting of mesoderm.
Deuterostomes develop the anus first, radial cleavage, and coelom develops from inpocketing of mesoderm.

Coeloms

A coelom is an interior body cavity that's crucial to the body plan of many animal phyla.
It's lined with mesoderm.
The fluid-filled space separates the gut from the rest of the body, allowing for organ specialization.
Coeloms can also serve as hydrostatic skeletons and for gamete storage. (acoelomate, coelomate, pseudocoelomate examples are given in the slides).

Lophotrochozoa

Includes many phyla that share a common ancestor that lived long ago.
Members exhibit a lophophore (feeding structure), trochophore larvae, or 18s RNA sequences suggestive of close relationships.

Platyhelminthes

Flatworms are unsegmented acoelomates with three tissue layers.
They lack a body cavity.
Nutrients and gases move via diffusion.
They have a non-respiratory and non-circulatory system.
They are free-living or parasitic.

Nemertea

Ribbon worms are marine, freshwater, and sometimes terrestrial.
They are important marine predators and scavengers.
A coelom stores the proboscis, which can evert for prey capture.
They have a mouth, an anus, vessels for circulation, flame cells for excretion, a brain and paired ventral nerve cords, and pigment cup ocelli.
They are also equipped with chemosensory organs.

Mollusca

Includes chitons, clams, snails, slugs, squids, and octopuses.
A major animal phylum with roughly 85,000 extant species (about 23% of named marine species).
Includes freshwater, marine and terrestrial species.
"Typical" features of mollusks include a coelom, often functioning as a hydrostatic skeleton, a mostly open circulatory system, heart, excretory system with nephridia, muscular foot, a shell, mantle cavity, and radula.
Also undergoes metamorphosis from a trochophore larva.
Major mollusk groups are Cephalopoda, Gastropoda, and Bivalva.

Annelida

Segmented worms are marine, freshwater, and terrestrial species.
They have a coelom forming a hydrostatic skeleton.
They have closed circulatory systems.
Includes polychaetes, oligochetes (mostly terrestrial burrowers), and hirundinea (leeches), and others (pogonophores).

Brachiopoda, Bryozoa, Rotifera

Lamp shells (Brachiopoda) are another lophotrochoate group.
Bryozoans are the largest phylum in the superphylum Lophotrochozoa.
Wheel bearers (Rotifera) are a very abundant group with many asexual lineages and uncertain affinities.

Ecdysozoa

A large group of protostomes that were discovered via 18s RNA analysis.
All members, in one way or another, shed their cuticles or exoskeletons.
Includes Nematoda, Nematomorpha, Onychophora, Tardigrada, and Arthropoda.

Nematoda

Roundworms are abundant, ecologically important ecdyzoans, and pseudocoelomates. (examples given; Caenorhabditis elegans and Ascaris lumbricoides)

Tardigrada

Water bears are incredibly resilient creatures able to withstand extreme conditions.

Arthropoda

Includes horseshoe crabs, arachnids, crustaceans, myriapods, and insects.
These organisms represent the largest phylum, with numerous species compared to other groups.
Features include segmented bodies, jointed appendages, and a cuticle made of chitin.
Chelicerates, Myriapods, Crustaceans, and Insects are subdivisions.
The body plan’s segmentation allows for specialization of certain segments.
Includes ventral nerve cords, dorsal guts, and open circulatory systems.
Tagmosis - progressive specialization and segment fusion. (examples given - Centipedes, Lobsters, Scorpion etc).
Crustacea(biramous appendages, most have gills as a ramet of leg); Marine, freshwater,terrestrial. Antennae and antennules; examples are given)
Insects - Terrestrial; Uniramous appendages; Three segmented body plan, six legs and two antennae; evolved from crustacean ancestor; tracheae as respiratory structures, many winged forms, many undergo metamorphosis; (example given - Mantistid lacewing)

Deuterostomia

Includes obvious developmental differences from other animal phyla; Chordates, Hemichordates, and Echinoderms.

Echinodermata

Starfish, brittle stars, urchins and sea cucumbers comprise this phylum.
Deuterostome phylum.
Secondary radial symmetry.
Features a water vascular system.

Chordata

The chordata phylum contains vertebrates, but also includes some invertebrates.
Key characteristics include a notochord at some point in their life, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail.
Subphyla include Urochordata (sessile filter feeders with pharyngeal slits), Cephalochordata (lancelets showing chordate features that feed and swim), Vertebrata.
Four anatomical features characterizing Chordata: Muscles segments, notochord, dorsal hollow nerve cord, brain and postanal tail; (examples given - Chordata diagram).

Vertebrata

Vertebrates have notable characteristics like the braincase.
Vertebral column is the core structure providing support, protection, enabling large size, fast movements, and protection of the nerve cord.
A closed circulatory system pumps oxygenated blood to cells, driving rapid metabolism and quick movement for searching for food and escaping predators.
Jawless vertebrates, the first radiation, includes hagfish; Lampreys (an early version of a vertebral column), and early fish. Subdivisions based on these characters are given)
Gnathostomes - a further division that have jaws; further subdivisions are given in slides.)

Tetrapods

Evolved from lobe-finned fish, early terrestrial tetrapods.
Earliest tetrapods were primarily aquatic and air breathers.
The "amphibian" assemblage diversified during the Carboniferous Period.
Many of those groups, probably tied to water for reproduction.
Contemporary amphibians and amniotes evolved from separate groups

Amniotes

Includes reptiles, mammals, and birds.
The amniotic egg is crucial for survival in arid terrestrial environments.
Specialized extraembryonic membranes (amnion, chorion, allantois) support gas exchange, waste storage, and nutrient transfer during development.
Gastrulation occurs with modifications for the large yolk.
Amniotes split into several groups early on, retaining the anapsid condition, with Synapsid and Sauropsid being prominent groups, leading to mammals, reptiles, and birds.

Reptiles

Reptiles are a paraphyletic assemblage of sauropsid amniotes.
Reptiles have keratin scales, and waterproof skin preventing water loss.
Unlike amphibians, reptiles breathe entirely through lungs.
Archosaurs include crocodilians, birds, and non-avian dinosaurs; there were other extinct relatives as well.
Birds (class Aves) are the lone survivors of dinosaur lineage; key characteristics include porous skeletons, unidirectional air flow in lungs, avian wings and feathers, and toothlessness.

Synapsids and Mammals

Synapsids diverged early from amniotes, diversifying into "mammal-like reptiles" and becoming ecologically dominant during the Permian.
Early synapsids likely possessed differentiated teeth and were homeothermic.
Mammals emerged in the early Jurassic, being abundant during the Mesozoic, diversifying into ecological niches after mass extinction.
Key mammalian traits are mammary glands, large brains, hair/subcutaneous fat, endothermy, and a dentary bone.
Three surviving groups include monotreme, marsupial, and eutherians.

Primates

Primates diversified in the Eocene epoch, approximately 50 million years ago.
One primate group gave rise to the apes, including humans.

Polling Questions

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Description

Test your knowledge on the Eumetozoa group and embryonic development stages. This quiz covers key characteristics of various animal phyla, including Cnidaria, Chordata, and Arthropods. Challenge yourself with questions about evolutionary features and developmental biology.