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Questions and Answers
What does taxonomy primarily involve?
What does taxonomy primarily involve?
Which of the following is NOT one of the six kingdoms of life?
Which of the following is NOT one of the six kingdoms of life?
What is a key characteristic of eukaryotic cells compared to prokaryotic cells?
What is a key characteristic of eukaryotic cells compared to prokaryotic cells?
What does the term 'endosymbiosis' refer to?
What does the term 'endosymbiosis' refer to?
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Which of the following statements about the origin of multicellularity is true?
Which of the following statements about the origin of multicellularity is true?
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The DNA sequence of the mitochondrial genome is most similar to which of the following?
The DNA sequence of the mitochondrial genome is most similar to which of the following?
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What is a major feature of phylogenetic trees?
What is a major feature of phylogenetic trees?
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Which of the following is NOT evidence for the endosymbiotic origin of organelles?
Which of the following is NOT evidence for the endosymbiotic origin of organelles?
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What is a major drawback of increasing body size in animals concerning gas and nutrient exchange?
What is a major drawback of increasing body size in animals concerning gas and nutrient exchange?
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Which statement correctly describes counter current exchange in aquatic animals?
Which statement correctly describes counter current exchange in aquatic animals?
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What mechanism do air-breathing insects utilize for gas exchange?
What mechanism do air-breathing insects utilize for gas exchange?
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Why is cutaneous gas exchange common in small and flat animals?
Why is cutaneous gas exchange common in small and flat animals?
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Which of the following structures is primarily responsible for gas exchange in aquatic animals?
Which of the following structures is primarily responsible for gas exchange in aquatic animals?
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In which way have some fish adapted their lungs for buoyancy?
In which way have some fish adapted their lungs for buoyancy?
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What is a functional disadvantage of the two-stroke buccal pump used by amphibians?
What is a functional disadvantage of the two-stroke buccal pump used by amphibians?
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What allows insects with large sizes to have limitations in their respiratory processes?
What allows insects with large sizes to have limitations in their respiratory processes?
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What is the primary way birds efficiently exchange gases during respiration?
What is the primary way birds efficiently exchange gases during respiration?
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What physiological adaptation do whales have to avoid the bends while diving?
What physiological adaptation do whales have to avoid the bends while diving?
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Why do bony fish face higher energy costs in maintaining osmotic balance in seawater?
Why do bony fish face higher energy costs in maintaining osmotic balance in seawater?
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Which statement correctly describes the blood flow in bird lungs?
Which statement correctly describes the blood flow in bird lungs?
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How do marine animals typically maintain differences between extracellular and external environments?
How do marine animals typically maintain differences between extracellular and external environments?
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What characterizes the extracellular environment for most marine organisms?
What characterizes the extracellular environment for most marine organisms?
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When mammals surface from a deep dive, what happens to the pressure experienced by gases in their body?
When mammals surface from a deep dive, what happens to the pressure experienced by gases in their body?
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What is one main role of the circulatory system in maintaining homeostasis?
What is one main role of the circulatory system in maintaining homeostasis?
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What is the primary purpose of the chemicals produced by the egg's surface?
What is the primary purpose of the chemicals produced by the egg's surface?
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In terms of fertilization environments, which organisms primarily use internal fertilization?
In terms of fertilization environments, which organisms primarily use internal fertilization?
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What initiates the activation of an inactive egg during fertilization?
What initiates the activation of an inactive egg during fertilization?
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What type of sperm structure facilitates its entry through the egg's jelly coat?
What type of sperm structure facilitates its entry through the egg's jelly coat?
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What happens to the sperm's tail once it enters the egg?
What happens to the sperm's tail once it enters the egg?
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How are the pronuclei of the egg and sperm involved in fertilization?
How are the pronuclei of the egg and sperm involved in fertilization?
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What is the role of the calcium ions released during fertilization?
What is the role of the calcium ions released during fertilization?
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What is a spermatophore?
What is a spermatophore?
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What is a key challenge faced by aquatic and marine plants in gas exchange?
What is a key challenge faced by aquatic and marine plants in gas exchange?
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How do aquatic plants primarily take up CO2?
How do aquatic plants primarily take up CO2?
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What role does turgor pressure play in plant cells?
What role does turgor pressure play in plant cells?
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What type of xylem structure do gymnosperms possess?
What type of xylem structure do gymnosperms possess?
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What initiates the opening of stomata in plant leaves?
What initiates the opening of stomata in plant leaves?
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Which statement correctly describes the role of osmotic potential in plants?
Which statement correctly describes the role of osmotic potential in plants?
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What is the characteristic pH range of seawater?
What is the characteristic pH range of seawater?
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What is the primary mechanism of water transport in plants?
What is the primary mechanism of water transport in plants?
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Study Notes
Taxonomy and Phylogeny
- Taxonomy involves identifying, describing, naming, and classifying species using a hierarchical system: Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species.
- Taxonomic classification groups organisms based on shared characteristics, creating order. However, these groupings aren't always clear-cut.
- Phylogeny, or evolutionary tree, represents a hypothesis of evolutionary relationships between organisms.
- A phylogenetic tree contains tips (taxa), nodes (branching points), and a root (common ancestor).
- There are currently six kingdoms: Protista, Fungi, Archaea, Bacteria, Plantae, and Animalia.
Tree of Life
- The current view of the tree of life primarily divides organisms into Bacteria and Archaea, with Eukaryotes forming a separate branch that descended from an archaean ancestor.
- This understanding is based on genomic sequencing evidence.
- The ancestor of all life is believed to have been a heterotrophic, unicellular prokaryote with peptidoglycan cell walls.
Origin of Eukaryotic Cells
- Eukaryotic cells emerged approximately 1-2 billion years ago.
- More complex than prokaryotes with distinct features like linear DNA in a nucleus, cell communication networks, and membrane-bound organelles such as chloroplasts and mitochondria.
- Endosymbiosis theory explains how eukaryotic cells evolved:
- Two independent bacterial species established a symbiotic relationship within a larger cell.
- The smaller cell benefited from protection and the larger cell gained energy and food.
- This relationship became obligate over time.
- Evidence for endosymbiosis includes:
- Membrane-bound organelles within eukaryotic cells.
- Mitochondria and chloroplasts contain their own circular genomes.
- DNA sequences of chloroplasts closely resemble those of Cyanobacteria.
- DNA sequences of mitochondria are similar to Proteobacteria.
Origin of Multicellularity
- Two main methods drive the origin of multicellularity:
- "Stay together" scenario: Clonal cells remain linked after mitotic division, creating a multicellular organism. This likely occurred due to mutations.
- Specialized cells: Cells developed different functions, enabling the formation of tissues and organs.
Diffusion in Multicellular Organisms
- Diffusion is crucial for gas and nutrient exchange within an organism.
- Diffusion efficiency is affected by body size.
- Large organisms have challenges in diffusion; smaller and flatter ones rely on diffusion while large organisms evolved complex circulatory systems.
- Aquatic animals can utilize cutaneous gas exchange (through skin) for gas exchange, while terrestrial animals need specialized structures like lungs.
Surface Respiratory Structures in Animals
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Air-breathing insects:
- Possess a trachea system, which is a network of rigid, internal branching tubes that transport oxygen and carbon dioxide through diffusion.
- The system is efficient for smaller insects but becomes less effective for larger ones.
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Aquatic animals:
- Utilize evaginated gills: External, often protected by a carapace, facilitate oxygen exchange and involve countercurrent exchange for maximum efficiency.
- Countercurrent exchange occurs when the flow of water and blood is in opposite directions, maximizing gas exchange, salt transport, heat transfer, and metabolite exchange.
- Gill anatomy: Water enters the mouth, passes through gill arches bearing filaments covered in lamellae. Lamellae are the sites of gas exchange.
- Co-current exchange (water and blood flow in the same direction) leads to equalized levels and is less efficient than countercurrent exchange.
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Air-breathing animals (terrestrial):
- Developed invaginated lungs: Internal structures that developed as outpocketings from the gut.
- They initially served for both air breathing and nutrient absorption.
- The opening is called a pneumostome.
- Air movement is facilitated through the body wall compression.
-
Evolution of lungs in fish:
- Lungs have been modified into swim bladders for buoyancy regulation in some fishes.
- Some fish have reconverted swim bladders back to lungs for air breathing.
- Other fish absorb oxygen through the gut while consuming food (air gulping).
- Some fish even use modified gills, skin, or gut for breathing.
Mammals and the Bends
- Gases dissolved in body fluids can form bubbles when the pressure decreases, causing the bends (decompression sickness).
- Whales avoid this by collapsing their lungs during dives, preventing gas exchange.
- They breathe a lot before dives to store oxygen and rely mostly on dissolved gases in their blood, making their breathing less frequent.
Circulatory Systems
- Internal environment refers to the inside of cells (intracellular), while external environment refers to the environment the organism lives in.
- The extracellular environment is the fluid surrounding cells, which is often different in composition and concentration from the intracellular environment.
- To maintain proper cellular function, the body must control water levels, solute levels, pH, and temperature, all while facing environmental challenges like temperature fluctuations and salinity changes.
- Fluid flow in tubes, such as blood vessels, is governed by physics, and different circulatory systems evolve to suit different needs.
- Open circulatory systems: Blood flows through a network of vessels, but it is partially contained within these vessels, and sometimes it mixes freely with the interstitial fluid.
- Closed circulatory systems: Blood is entirely contained within vessels, allowing efficient transport and pressure control.
Gravity and Blood Pressure
- Gravity plays a role in blood pressure, as it pulls blood downward.
- Blood pressure must be sufficient to overcome gravity and deliver blood to the entire body.
- The circulatory system has mechanisms to maintain blood pressure, such as pulsatile pumping and the elasticity of blood vessels.
- Higher organisms, evolving larger bodies, require more efficient blood delivery and pressure control.
Fertilization
- Fertilization occurs when the egg and sperm fuse, resulting in the formation of a zygote.
- Sperm has several challenges:
- Finding the egg.
- Identifying the correct egg (species-specific).
- Preventing other sperm from fertilizing the egg.
- Internal fertilization: Occurs inside the female's body, providing a more protected environment and increasing the likelihood of successful fertilization.
- External fertilization: Takes place outside the body, usually in water, and often involves releasing many sperm and eggs.
Egg Activation
- A sperm activates the egg by fusing with its plasma membrane.
- The egg resumes metabolic activity and prepares for development.
Nuclear Fusion
- The egg and sperm pronuclei fuse, producing a diploid zygote containing genetic material from both parents.
- The sperm's acrosomal enzymes dissolve the egg's outer layers.
- The sperm’s acrosomal process penetrates the egg jelly coat to reach the egg's plasma membrane, allowing the sperm's nucleus to enter the egg.
- The sperm tail and mitochondria are discarded.
Fertilization Barriers
- The egg releases calcium ions, creating an electrical barrier that repels other sperm.
- The egg releases cortical granules, which form a fertilization membrane that prevents further sperm entry.
Plant Water Relations
- Plant water relations refer to how plants regulate water content, including uptake, transport, and loss.
- Water Potential: The potential energy of water in a system, influenced by factors like osmotic potential, turgor pressure, and matric potential.
- Osmotic Potential: The potential energy of water due to differences in concentration across a semipermeable membrane.
- Turgor Pressure: The hydrostatic pressure of water within a cell, crucial for cell expansion and growth.
- Flaccid Cells: Cells with low turgor pressure.
- Turgid Cells: Cells with high turgor pressure, resulting in cell expansion.
- Stomata: Pores on leaves that regulate gas exchange and water loss (transpiration).
- Root Pressure: The pressure of water within the roots that contributes to water movement upward in the plant.
- Guttation: The exudation of water droplets from leaf tips or margins due to root pressure.
- Xylem: The vascular tissue in plants that transports water from the roots to the leaves.
- Tracheids: The elongated, dead, tube-like cells that make up the xylem of gymnosperms.
- Vessels: A series of connected, dead, tube-like cells that make up the xylem of angiosperms.
- Capillary Forces: The forces between water molecules and the walls of the xylem vessels, contributing to water transport.
- Negative Xylem Pressures (Suction Tension): The force that pulls water upward in the xylem, driven by transpiration from the leaves.
- Cavitation: The formation of air bubbles in the xylem vessels, which can disrupt water flow.
- Stomata Open: Guard cells absorb ions and water, increasing turgor and opening the pores.
- Stomata Close: Guard cells lose ions and water, decreasing turgor and closing the pores.
- Stomata first appeared: At least 400 million years ago, playing a critical role in gas exchange and regulating water loss.
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Description
Test your knowledge on taxonomy and phylogeny with this quiz! Explore the classification of species, understand the hierarchical system used in taxonomy, and learn about the evolutionary relationships depicted in phylogenetic trees. Dive into the tree of life and discover the six kingdoms of organisms.
