Biology Chapter: Organisms and Eukaryotic Features

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Questions and Answers

Which of the following theories suggests that multicellularity arose from different unicellular organisms living together in a symbiotic relationship?

Symbiotic theory (correct)

Syncytial theory

Colonial theory

Evolutionary theory

What is the role of tight junctions in multicellular organisms?

They connect cells to the extracellular matrix

They enable movement of cells

They allow for cell differentiation

They fix cells in place and prevent movement (correct)

Which statement best describes the colonial theory of multicellularity?

It begins with flagellated unicellular organisms of the same species forming colonies. (correct)

It suggests that cells must maintain a constant state of communication.

It proposes that a single cell divides without cytokinesis.

It involves the aggregation of genetically different cells.

Which of the following is NOT a factor necessary for the evolution of multicellularity?

Cells' ability to move freely in the environment Signup and view all the answers

What significant event brought about higher levels of oxygen and contributed to the emergence of simple multicellularity?

The rise of cyanobacteria Signup and view all the answers

What defines a eukaryotic organism?

It possesses membrane-bound organelles. Signup and view all the answers

What is the primary function of the cytoskeleton in eukaryotic cells?

To support cell shape and enable movement. Signup and view all the answers

Which of the following is NOT a characteristic feature of eukaryotic cells?

Looped DNA structure. Signup and view all the answers

What role does the endomembrane system play in eukaryotic cells?

It compartmentalizes the cell to increase surface area for synthesis. Signup and view all the answers

Which of the following differentiates prokaryotes from eukaryotes?

Prokaryotes possess 70s ribosomes. Signup and view all the answers

Why is the linear structure of eukaryotic chromosomes beneficial?

It facilitates complex gene regulation. Signup and view all the answers

What is a unique feature of plastids found in plant cells?

They function in photosynthesis and storage. Signup and view all the answers

What characteristic of eukaryotic gametes allows for genetic variation?

They fuse during fertilization. Signup and view all the answers

What primarily differentiates land plants from fungi?

Land plants can produce their own food. Signup and view all the answers

Which statement about Monotropa uniflora is true?

It lacks chlorophyll and is heterotrophic. Signup and view all the answers

What is the role of turgor pressure in plant cells?

It provides rigidity by pushing against the cell wall. Signup and view all the answers

What characteristic is unique to some plant cells regarding their structural components?

They contain lignin in their cell wall. Signup and view all the answers

What is a primary function of vacuoles in plant cells?

They provide structural integrity through water balance. Signup and view all the answers

How does the secondary cell wall contribute to a plant's structure?

It acts as a waterproof barrier and increases rigidity. Signup and view all the answers

In what type of solution do plant cells typically become turgid?

Hypotonic solution. Signup and view all the answers

What is the main component of cellulose found in plant cell walls?

Polymers of glucose that are unbranched. Signup and view all the answers

Which of the following statements accurately describes gametes in land plants?

Gametes are produced by sporophytes and are haploid. Signup and view all the answers

In the life cycle of land plants, after fertilization, what happens to the embryo?

It is retained in the female gametophyte tissue. Signup and view all the answers

What role does lignin play in vascular plants?

It serves to increase height and rigidity of vascular tissue. Signup and view all the answers

Which of the following statements about non-vascular plants is true?

They lack vascular tissue and have a dominant haploid generation. Signup and view all the answers

Which group of plants is characterized by having vascular tissue and seeds?

Vascular seed plants Signup and view all the answers

What is the primary function of stomata in land plants?

Gas exchange Signup and view all the answers

Which structure is responsible for preventing water loss in land plants?

Waxy cuticle Signup and view all the answers

How do guard cells contribute to stomatal function?

They regulate turgor pressure Signup and view all the answers

Which adaptation allows vascular plants to grow taller and transport water effectively?

Vascular tissue Signup and view all the answers

What distinguishes non-vascular plants such as mosses in terms of their reproductive structures?

Rhizoids instead of roots Signup and view all the answers

In which group of plants did non-swimming sperm first appear?

Gymnosperms Signup and view all the answers

Which plant feature evolved last in the provided evolutionary timeline?

Flowers and ovaries Signup and view all the answers

What is the relationship between the length of the sporophyte stage and its relative size in different plant groups?

Mosses have shorter sporophytes than ferns Signup and view all the answers

What is a key advantage of multicellularity that aids in predator avoidance?

Increased size Signup and view all the answers

Which adaptation is essential for increasing surface area in gas exchange?

High folds in respiratory structures Signup and view all the answers

What is a disadvantage linked to multicellularity?

Increased predator/prey interactions Signup and view all the answers

Which process must occur in multicellular organisms for reproduction and growth?

Fusion of gametes Signup and view all the answers

What challenge does increasing size present to multicellular organisms?

Decreased surface area relative to volume Signup and view all the answers

Which structure is crucial for intercellular communication in larger multicellular organisms?

Nerves Signup and view all the answers

What type of tissue in animals arises from all three embryonic germ layers?

All epithelial tissues Signup and view all the answers

What is the primary function of homeostasis in multicellular organisms?

Maintaining stable internal conditions Signup and view all the answers

What is the significance of the double membrane structure in mitochondria and plastids?

It suggests a complex endosymbiotic origin. Signup and view all the answers

What is a primary hypothesis regarding how mitochondria originated in eukaryotic cells?

A heterotrophic eukaryotic cell engulfed an aerobic proteobacterium. Signup and view all the answers

In the context of cell size, what does the cube-square relationship explain?

Smaller cells have a greater surface area relative to their volume. Signup and view all the answers

What is the role of the endomembrane system in eukaryotic cells?

To facilitate protein synthesis and transport. Signup and view all the answers

What is a key characteristic of eukaryotic cells compared to prokaryotic cells?

Eukaryotic cells possess membrane-bound organelles. Signup and view all the answers

Which type of multicellularity is characterized by cell adhesion and communication without fluid movement?

Simple multicellularity. Signup and view all the answers

How do smaller cells exhibit advantages in material exchange?

By having a smaller volume relative to surface area. Signup and view all the answers

What is the role of secondary endosymbiosis in cellular evolution?

It allows for the merging of different eukaryotic lineages. Signup and view all the answers

Which of the following correctly distinguishes prokaryotes from eukaryotes?

Eukaryotes possess a true nucleus. Signup and view all the answers

What advantage does the linear structure of eukaryotic chromosomes provide?

Facilitates complex gene regulation. Signup and view all the answers

What is a primary function of the cytoskeleton in eukaryotic cells?

Support cell shape and facilitate movement. Signup and view all the answers

Which of the following is a characteristic of eukaryotic cells?

They can be either unicellular or multicellular. Signup and view all the answers

What is the primary role of the endomembrane system in eukaryotic cells?

To compartmentalize cellular processes for efficiency. Signup and view all the answers

Which structure is primarily responsible for the movement of eukaryotic cells?

Cilia and flagella. Signup and view all the answers

What type of DNA is typically found in prokaryotic organisms?

Circular DNA usually in a single strand. Signup and view all the answers

Which feature is unique to eukaryotic organisms compared to prokaryotes?

Existence of membrane-bound organelles. Signup and view all the answers

What is a characteristic of the secondary cell wall in some plants?

It creates a waterproof barrier for the plant. Signup and view all the answers

Which of the following is true regarding the water balance in plant cells?

Water enters plant cells primarily through osmosis. Signup and view all the answers

What distinguishes land plants from fungi?

Land plants primarily use photosynthesis to create their own food. Signup and view all the answers

How does breech cell wall structure contribute to plant cell features?

Cell walls provide tensile strength and flexibility. Signup and view all the answers

What is the role of the vacuole in plant cells?

It is a membrane-bound organelle for water balance. Signup and view all the answers

What is true about Monotropa uniflora?

It is dependent on other plants for nutrients due to its lack of chlorophyll. Signup and view all the answers

How does the alternation of generations differ in land plants compared to animals?

Land plants have multicellular haploid and diploid stages. Signup and view all the answers

What feature makes cellulose particularly important for plants?

It is the most abundant organic polymer providing structural integrity. Signup and view all the answers

What is the primary role of pollen in gymnosperms?

To transfer sperm to the ovule Signup and view all the answers

In angiosperms, what process occurs during double fertilization?

One sperm fertilizes an egg and another fertilizes two nuclei Signup and view all the answers

Which of the following describes the dominant phase in gymnosperms?

Sporophyte phase Signup and view all the answers

Which characteristic distinguishes monocots from eudicots?

Presence of parallel leaf veins Signup and view all the answers

What is the significance of seed dormancy in plants?

To protect the embryo until conditions are favorable Signup and view all the answers

Which feature is unique to angiosperms compared to gymnosperms?

Formation of flowers Signup and view all the answers

How do megaspores contribute to the female reproductive structure of gymnosperms?

They develop into female gametophytes inside the ovule Signup and view all the answers

What helps guide pollen from male cones to female ovules in gymnosperms?

Mature pollen wings Signup and view all the answers

What are choanoflagellates?

Unicellular opisthokonta eukaryotes. Signup and view all the answers

Which of the following is a characteristic of choanoflagellates? (Select all that apply)

They reproduce asexually Signup and view all the answers

Choanoflagellates are motile organisms.

True Signup and view all the answers

What is a clade?

A monophyletic group with shared derived traits Signup and view all the answers

Animals with bilateral symmetry have _________ symmetry.

mirror-image left-right Signup and view all the answers

Which of the following describes diploblastic animals?

They have two embryonic tissue layers. Signup and view all the answers

What are protostomes?

Animals whose first opening in the embryo becomes the mouth. Signup and view all the answers

What is metameric segmentation?

Repetition of body segments. Signup and view all the answers

Which phylum includes creatures known as comb jellies?

Phylum Ctenophora Signup and view all the answers

Cnidarians are classified as diploblastic animals.

True Signup and view all the answers

The body plan of a mollusk is organized into a foot, mantle, and ________.

viscera Signup and view all the answers

What defines echinoderms?

Pentaradiate symmetry as adults Signup and view all the answers

Match the following phyla with their characteristics:

Cnidaria = Radial symmetry, diploblastic Porifera = Asymmetrical, filter feeders Chordata = Notochord, dorsal hollow nerve cord Arthropoda = Jointed limbs, segmented body Signup and view all the answers

Study Notes

Organisms and their Characteristics

Organisms are either made up of a single cell (like bacteria) or multiple cells (like plants and animals).
The living world hierarchy classifies different levels of organization from ecosystems to atoms.
Major divisions of the living world are defined by different characteristics like presence or absence of nucleus and cell structure.
Bacteria are single-celled organisms without a nucleus and gave rise to mitochondria.
Archaea are similar to bacteria.
Eukarya have a nucleus and can be single or multicellular.

Eukaryotic Features

Eukaryotic cells have a nucleus, membrane organelles, and large 80s ribosomes.
Cytoskeleton: Provides cell support and shape using protein fibers, enabling phagocytosis.
Microtubules: Hollow tubes formed from tubulin dimers.
Microfilaments: Double helix of actin monomers for movement and transport.
Intermediate filaments: Made from proteins for structural support.
Cilia: Short and numerous, helping to move fluid or the cell.
Flagella: Long and work in pairs to propel the cell forward.
Endomembrane system: A collective term for nuclear envelope, lysosomes, Golgi apparatus, vacuoles, and endoplasmic reticulum.
Linear DNA: Multiple linear strands of DNA promote complex gene regulation, cellular differentiation, and tissue formation.
Gamete Fusion: Involves the fusion of gametes for reproduction.
Plastids: Found in plants for photosynthesis.

Prokaryotes

Single loop of DNA, good for rapid replication but simple gene regulation.
70s ribosomes (similar to mitochondria).

Multicellular Life

Cells in multicellular organisms adhere, communicate, differentiate, and specialize for specific functions.
Multicellularity arose independently at least six times.

Theories of Multicellularity

Symbiotic Theory: Different unicellular organisms live together in a symbiotic relationship and specialize to form a single organism.
Syncytial Theory: One cell divides into multiple cells without cytokinesis and then differentiates.
Colonial Theory: A group of flagellated unicellular organisms of the same species form colonies and differentiate.

Evolution of Multicellularity

The Great Oxygenation Event, caused by cyanobacteria photosynthesis, led to increased oxygen levels and the emergence of complex animals.
Simple and complex multicellularity arose at different points in the event.

Cell Adhesion and Differentiation

Cell adhesion involves cells sticking together to form tissues.
Tight junctions: Penetrate cell membranes, fix cells, and prevent movement.
Anchoring junctions: Link cells together and to microfilaments.
Differentiation: Cells becoming specialized for specific functions.

Importance of Multicellularity

Multicellularity offers advantages like specialization and complexity but poses challenges like slower movement and susceptibility to environmental changes.

Characteristics of Land Plants

Eukaryotes
Primarily photoautotrophs, but not always.
Multicellular.
Sessile or stationary.
Cell walls.
Alternation of generations life cycle.
Embryo (sporophyte) retained on the gametophyte tissue.

Plant Cell Features

Primary cell wall surrounding the plasma membrane and cell contents.
Cellulose fibers for rigidity and flexibility.
Secondary cell wall in some plants for additional rigidity (xylem, sclerenchyma).
Lignin in secondary cell wall for waterproofing and increased rigidity.

Turgor Pressure

Turgor pressure provides rigidity by pushing against the cell wall.
Hypotonic conditions lead to water moving into the cell, making it turgid.
Hypertonic conditions lead to water moving out of the cell.
Vacuole plays a crucial role in water balance.

Plant Life Cycle vs. Animal Life Cycle

Plants have a dominant diploid individual.
Gametes (haploid) are formed through meiosis.
Gametes are not free-living.

Alternation of Generations

Sporophyte (2n): Produces spores (n) through meiosis.
Spores (n): Haploid, unicellular, and make gametophytes (n) through mitosis.
Gametophytes (n): Multicellular, produce unicellular gametes.
The embryo (2n) is retained in the female gametophyte tissue after fertilization.

Land Plant Classification

Vascular Tissue: Xylem, phloem, parenchyma cells, and fiber cells.
Xylem: Dead at maturity, conducts water.
Phloem: Live cells, transport sugar.
Seeds: Contain cotyledons, stem cell zone, and radical (undifferentiated cells).
Seed ferns: First to evolve seeds.

Non-vascular Plants

First to evolve.
Lack vascular tissue.
Haploid generation is dominant.
Less rigidity.
Examples: Bryophytes

Vascular Seedless Plants

Have vascular tissue but no seeds.
Diploid generation is dominant.
Examples: Lycophytes

Vascular Seed Plants

Have vascular tissue and seeds.
Last to evolve.
Diploid dominance.
Lignin fibers increase development and support.
Examples: Gymnosperms (conifers).

Importance of Land Plants

Provide oxygen, drugs, food, fiber, timber, and ecosystem services.

Adaptations to Dry Conditions on Land

Waxy Cuticle: Prevents water loss.
Stomata: Pores for gas exchange, controlled by guard cells.
Vascular Tissue: Thickened cell walls with lignin, allow vertical growth and water transport.
Root System: Rhizoids in non-vascular plants, roots in vascular plants.

Evolution of Land Plant Adaptations

Stomata was present in mosses (non-vascular plants).
Vascular tissues with lignified cells and leaves evolved in lycophytes.
Non-swimming sperm and seeds evolved in gymnosperms.
Flowers and ovaries evolved in angiosperms.

Evolutionary Timeline and Adaptations

Plant Group	Water Availability	Free Living Zygote	Gametophyte Generation	Sporophyte Generation	Gametophyte Size	Sporophyte Size	Zygote/Embryo Protection
Algae	High	Yes	Long	Short	Large	Small	Low
Mosses	Moderate	No	Long	Short	Large	Small	Moderate
Ferns	Moderate	No	Short	Long	Small	Large	Moderate
Conifers (Gymnosperm)	Low	No	Very Short	Very Long	Very Small	Very Large	High

Organism and Levels of Living World

An organism can be single-celled or multicellular.
Single-celled organisms include bacteria.
Multicellular organisms include plants and animals.
The levels of the living world hierarchy are: ecosystem, community, population, organism, organ, tissue, cells, molecule, and atom.
The major divisions of the living world are defined by characteristics such as the presence or absence of a nucleus and cell wall.
- Bacteria are single-celled organisms with no nucleus and gave rise to mitochondria.
- Archaea share similarities with bacteria.
- Eukarya have a nucleus and can be single or multicellular.

Eukaryotes

Eukaryotic cells have a nucleus, membrane-bound organelles, and large 80s ribosomes.
Eukaryotes have a cytoskeleton that supports cell shape and controls membranes.
- The cytoskeleton consists of protein fibers including microtubules, microfilaments, and intermediate filaments.
- Microtubules are hollow tubes formed from tubulin dimers.
- Microfilaments are double helices of actin monomers involved in movement and transport.
- Intermediate filaments are made of proteins for support.
Eukaryotes have cilia and flagella for movement.
- Cilia are shorter and aid in fluid movement or cell movement.
- Flagella are longer and work in pairs to propel the cell forward.
The endomembrane system in eukaryotes includes the nuclear envelope, lysosomes, Golgi apparatus, vacuoles, and the endoplasmic reticulum.
- It compartmentalizes the cell's interior and increases surface area for synthesis.
Eukaryotic cells have multiple, linear DNA molecules.
- They undergo gamete fusion for sexual reproduction.
- They contain plastids, such as chloroplasts, in plants.

Prokaryotes

Prokaryotes have a single loop of DNA, suitable for rapid replication but with simple gene regulation.
They possess 70s ribosomes (similar to those in mitochondria).

The Advantage of Eukaryotic Linear Chromosomes

Linear chromosomes allow for complex gene regulation, cell differentiation, and the production of diverse tissue types.
All chromosomes replicate in parallel.

Mitochondria

Mitochondria are the sites of oxidative phosphorylation.
They are responsible for cellular energy production using food to make ATP.
Eukaryotic cells also have chloroplasts for photosynthesis.
Mitochondria increase the surface area for energy production.

Sexual Reproduction

Sexual reproduction is exclusive to eukaryotes.
It involves the fusion of haploid gametes from two parents to produce genetically diverse offspring.

Endosymbiotic Origin of Mitochondria and Plastids

Evidence for the endosymbiotic origin includes:
- Circular DNA.
- Independent fission (removal of mitochondria or plastids from the eukaryotic cell).
- Smaller size compared to eukaryotes.
- Double membrane.
- 70s ribosomes.
Primary Hypothesis 1: A heterotrophic eukaryotic cell engulfed an aerobic proteobacterium, leading to a mutualistic relationship that formed the mitochondria.
Primary Hypothesis 2: A heterotrophic eukaryotic cell engulfed a photosynthetic cyanobacterium, which became the chloroplast.

Alternative Scenarios for Eukaryotic Cell Evolution

Scenario 1: An archaeon developed an endomembrane system before acquiring a mitochondrion.
Scenario 2: An archaeon engulfed the mitochondrion and then developed the endomembrane system.
- This is more plausible because mitochondria would have provided the energy for the formation of other organelles.
Horizontal gene transfer transferred prokaryotic genes to the eukaryotic nucleus.

Secondary Endosymbiosis

A heterotrophic eukaryotic cell engulfed an autotrophic eukaryotic cell.

Cell Size

Eukaryotic cells are larger than prokaryotic cells.
The cube-square relationship states that as an object grows larger, its volume increases faster than its surface area.
- The rate of material exchange is determined by the surface area.
- The rate of gas and nutrient usage and waste production is determined by the volume.
Smaller cells exchange materials more effectively due to the surface area to volume ratio.
Diffusion and active transport are limited by distance.
Membrane folding in mitochondria, Golgi, and plastids enhances material entry and protein production.

Types of Multicellularity

Simple Multicellularity: Involves cell adhesion and communication but no bulk flow.
Complex Multicellularity: Uses bulk flow for the movement of fluids and gases.

Advantages of Multicellularity

Division of labor and economy of scale: Specialized cells perform specific tasks efficiently.
Increased size:
- Avoidance of predators.
- Exploitation of new environments including reaching upwards.
- Increased feeding opportunities.
- Creation of an internal environment.
Cellular specialization: Diverse cell types with unique functions.
New metabolic functions: Enhanced metabolic processes.
Enhanced motility: Improved movement capabilities.
Cell-to-cell communication: Sharing information and coordination.
Increased traction: Improved ability to resist wind or current.

Disadvantages of Multicellularity

Predator-prey interactions: Increased susceptibility to predators.
Host-parasite interactions: Increased vulnerability to parasitic infections.

Challenges of Being Large

Intercellular communication:
- Diffusion is limited to short distances.
- Gap junctions facilitate communication.
- Bulk flow aids in gas and liquid transport.
- Specialized nerves.
Cell adhesion: Maintaining connections between cells.
Surface area to volume ratio: As size increases, the surface area relative to volume decreases.

Structure and Support

Terrestrial animals have limitations in size.
Smaller animals lose heat faster.
Smaller animals have higher basal metabolic rates (BMR), while larger animals have lower mass-specific metabolic rates.

Adaptations for Increasing Surface Area

Gas exchange: Highly folded structures pack greater surface area into smaller volume.
Nutrient absorption: Villi in the small intestine increase surface area for absorption.
Filtration: Capillaries have high surface area for filtration.

Homeostasis

Homeostasis helps defend cells against harsh environments.
Extracellular fluid, the fluids outside the cells, must be kept stable.
Intracellular fluid refers to the fluids inside the cells.

Reproduction and Growth

Organisms need to reproduce and grow.
Unicellular organisms reproduce through fission or mitosis.
Multicellular organisms reproduce through gamete fusion.

Characteristics of Animals

Triploblastic development: Animals arise from three embryonic germ layers, resulting in four tissue types:
- Muscle tissue.
- Neural tissue.
- Epithelial tissue.
- Connective tissue.
Extracellular matrix: A network of proteins and polysaccharides that surrounds cells.
Collagen: An extracellular fibrous protein found in connective tissues.

Opisthokonts

Opisthokonts include animals, fungi, and choanoflagellates.
Choanoflagellates are free-living, single-celled eukaryotes.

Characteristics of Land Plants

Eukaryotic: Have a nucleus.
Photoautotrophic: Primarily produce food through photosynthesis but not always.
Multicellular: Composed of multiple cells.
Sessile: Stationary due to photosynthetic nature and roots.
Cell walls: Rigid structures surrounding the cell membrane.
Alternation of generations life cycle: Have both haploid and diploid stages.
Embryo retention: The sporophyte embryo is retained on the gametophyte tissues.
Monotropa uniflora: A heterotrophic plant lacking chlorophyll.
- Cannot produce its own food.

Plant Cell Features

Primary cell wall: Surrounds the plasma membrane and cell contents.
- Contains cellulose fibers.
- Provides flexibility and rigidity.
Secondary cell wall: Present in some plants, particularly in xylem and sclerenchyma cells.
- Cellulose fibers are reinforced with lignin, making it rigid and waterproof.
Turgor pressure: Pressure exerted by the vacuole against the cell wall, maintaining rigidity.
- Hypotonic solution results in water entering the cell, creating turgor pressure.
- Hypertonic solution causes water to leave the cell, leading to a decrease in turgor pressure.
Vacuole: A large, membrane-bound organelle that stores water and plays a crucial role in water balance.

Seed Plants

Seed plants: Have seeds and vascular tissue.
Gymnosperms: Naked seed plants.
- Dominate land terrains.
- The sporophyte phase is dominant.
Flowering plants (angiosperms): Plants that produce flowers and seeds.
- Ovary develops into a fruit.
- Ovule becomes a seed.
Monocots: Single cotyledon (seed leaf).
- Parallel leaf venation.
- Three petals.
Eudicots: Two cotyledons.
- Branching leaf venation.
- Four or more petals.
Double fertilization:
- First fertilization: One sperm cell from pollen fertilizes the egg cell, forming a zygote.
- Second fertilization: Another sperm cell fertilizes two nuclei in the ovule's central cell, forming a triploid cell that develops into the endosperm.

Angiosperm Reproduction

Megaspore formation in the ovary: The ovary contains ovules, each with a megasporophyll (mother cell) that undergoes meiosis to produce four megaspores.
- Three megaspores degenerate, and one functional megaspore divides mitotically three times, producing eight cells within the embryo sac.
- The embryo sac contains:
  - Three antipodal cells at the top.
  - Two synergids that guide the pollen tube.
  - One egg cell for fertilization.
  - Two polar nuclei at the center.
Pollen grain formation in the anther: The anther contains microspores that undergo mitosis to generate pollen grains.
- Each pollen grain contains two sperm cells.

Gymnosperm Reproduction

Male gametophyte (pollen): Pollen is released from male cones (microspores).
Female gametophyte: Megaspore develops into the female gametophyte inside the ovule (megasporangium), which contains the egg cell.
Pollination: Pollen is transferred to the female cone.
Fertilization: Sperm travels through a pollen tube to fertilize the egg cell.
Seed development: Fertilized egg develops into an embryo.

Phylum Coniferophyta

Conifers: Dominant group of gymnosperms.
Pines, firs: Examples of conifers.

Choanoflagellates

Unicellular eukaryotes that are most closely related to animals in the Opisthokonta group.
Sessile and reproduce asexually.
Have a collar around their flagellum with contractile microfibrils, similar to choanocytes found in sponges.
Filter feeders that consume bacteria.

Animals

Multicellular eukaryotes that are chemoheterotrophic.
Digest food extracellularly, lacking cell walls and are motile.
Obtain energy through oxidative phosphorylation.
Have a dominant diploid stage in their life cycle.
Developed from a blastula and underwent gastrulation.
Cell membranes contain cholesterol.
Possess extracellular matrix, including collagen.
Exhibit cell-cell junctions like tight, anchoring, and gap junctions.

Plants

Multicellular eukaryotes that are photoautotrophic.
Fix inorganic carbon using light energy.
Have cell walls for structural support and protection.
Sessile, with an alternation of generations between a haploid gametophyte and a diploid sporophyte.
Utilize large vacuoles for turgor pressure against the cell wall.
Contain chloroplasts.
Have limited motility but can disperse through pollen or seeds.

Fungi

Chemoheterotrophic organisms.
Most are mobile to acquire nutrients.
Exhibit traits that promote motility, including muscles, sense organs, cephalization, and specialized nervous, digestive, excretory, and skeletal systems.
Have a high metabolic rate but some fungi are sessile.
Dominant stage for fungi is diploid.

Clades

Clades are monophyletic groups that include all descendants of a common ancestor, sharing derived homologies called synapomorphies.
Provide the most parsimonious phylogeny, minimizing proposed evolutionary changes.

Early Animal Fauna

The first diverse fauna of large, complex multicellular animals.
The first fauna with eyes and jaws.
Homeotic genes regulate the development of anatomical structures.
Represent evolutionary radiation within the Animalia kingdom.

Animal Symmetry and Body Cavities

Asymmetry: No major axis of symmetry.
Radial Symmetry: Body can be divided into identical segments, lacking definite left/right or front/back.
Bilateral Symmetry: Body has mirror-image left-right symmetry.
Acoelomate: No cavity enclosing the gut.
Pseudocoelomate: A cavity enclosing the gut lined with mesoderm on the outer side only.
Coelomate: A cavity enclosing the gut lined with mesoderm on both sides.

Animal Embryonic Tissue Layers

Diploblastic: Two embryonic layers: endoderm and ectoderm.
Triploblastic: Three embryonic layers: endoderm, mesoderm, and ectoderm.

Bilaterian Development

Protostomes: The first opening in the embryo develops into the mouth.
Deuterostomes: The first opening in the embryo develops into the anus.

Metameric Segmentation

Repeated segments along the body axis, found in organisms like chordates, arthropods, and annelids.

Phylum Ctenophora (Comb Jellies)

Exhibit biradial symmetry.

Phylum Porifera (Sponges)

Asymmetrical.
Sessile as adults.
Lack nerves and are filter feeders.
Choanocytes facilitate flagellar action for feeding.
Suspension feeders.

Phylum Cnidaria (Jellyfish, Coral)

Radial symmetry.
Diploblastic.
Possess cnidocytes for prey capture.

Colonial Cnidarians

Examples include Siphonophores, which are a type of colonial marine cnidarian.

Protostomes

Two major groups based on development: Lophotrochozoans and Ecdysozoans.

Lophotrochozoans

Have a trochophore larva stage in their development.
Some possess a lophophore feeding structure.

Ecdysozoans

Possess an external cuticle that is shed (molted) during growth, a process called ecdysis.
The cuticle is acellular and secreted by epidermal cells.

Lophotrochozoan Phyla

Phylum Platyhelminthes (FlatWorms)

Acoelomate, lacking a cavity between the body wall and gut.
No circulatory system.

Phylum Mollusca (Mollusks)

Body organized into a foot, mantle, and visceral mass.
Unsegmented.

Phylum Annelida (Segmented Worms)

Exhibit metamerism (segmentation).
Well-defined segments along the body.

Ecdysozoan Phyla

Phylum Nematoda (Roundworms)

Pseudocoelomate - body wall lined with mesoderm, but the gut lacks a mesoderm envelope.
Unsegmented.

Phylum Arthropoda (Arthropods)

Possess a jointed chitinous exoskeleton.
Segmented body with distinct body parts.
Jointed limbs.
Tagmatization - fusion of body segments.

Deuterostomes

Phylum Echinodermata (Echinoderms)

Bilaterally symmetrical larvae.
Pentaradial symmetry as adults.
Water vascular system and tube feet for locomotion.

Phylum Hemichordata (Hemichordates)

Pharyngeal gill slits.
Dorsal nerve cord and a stomochord (a structure similar to a notochord).

Phylum Chordata (Chordates)

Notochord - a flexible rod that supports the body.
Dorsal hollow nerve chord.
Pharyngeal slits for filter feeding (often modified in vertebrates).
Post-anal tail.
Segmented muscles.

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Explore the characteristics of living organisms, including the distinction between prokaryotic and eukaryotic cells. This quiz covers topics such as cell structure, the living world hierarchy, and features of eukaryotic cells, including cytoskeleton components and their functions. Test your knowledge of the fundamental aspects of biology.