Biology 224 (Midterm) UPDATED ACTUAL Questions and CORRECT
Answers
Question: What is homeostasis?
Correct Answer: Regulation of the body's internal environment at or near a stable level.
Question: Why is homeostasis necessary?
Correct Answer: It allows organisms to maintain optimal physiological performance despite changes in
internal or external environments.
Question: What is the difference between regulators and conformers?
Correct Answer: Regulators maintain internal conditions regardless of external changes, while conformers
adjust their internal conditions to match external changes.
Question: What types of feedback are involved in homeostasis?
Correct Answer: Negative feedback, positive feedback, and feedforward.
Question: What is negative feedback?
Correct Answer: A mechanism that returns a variable toward a set point, minimizing the difference
between actual levels and the set point.
Question: How does negative feedback work in body temperature regulation?
Correct Answer: Endothermic animals use negative feedback to balance heat loss and gain, maintaining
body temperature near a set point.
Question: What is positive feedback?
Correct Answer: A mechanism that moves a variable away from the set point, amplifying the difference
until it is shut off by negative feedback.
Question: Give an example of positive feedback.
Correct Answer: Childbirth, where oxytocin stimulates labor.
Question: What is feedforward?
Correct Answer: A mechanism where future needs are anticipated and physiological adjustments are made
in advance.
Question: What is a fever?
Correct Answer: An elevated core body temperature as a defense response against pathogens, resulting
from a change in the internal set point.
Question: What happens during a fever?
Correct Answer: The hypothalamus raises the internal set point, activating the immune system to fight
infection.
Question: What are some variables regulated by homeostasis?
Correct Answer: Temperature, nutrients, oxygen, carbon dioxide, waste, water, salt, and pH.
Question: What is the goal of homeostasis?
,Correct Answer: To allow organisms to achieve optimal physiological performance.
Question: What is the difference between acoelomate, pseudocoelomate, and coelomate?
Correct Answer: Acoelomates lack a body cavity; pseudocoelomates have a fluid-filled cavity; coelomates
have a true body cavity lined with mesoderm.
Question: What are protostomes and deuterostomes?
Correct Answer: Protostomes develop the mouth first, while deuterostomes develop the anus first.
Question: What is cephalization?
Correct Answer: The concentration of sensory organs and nervous tissue at the anterior end of an
organism.
Question: What is segmentation?
Correct Answer: The division of the body into repetitive segments, allowing for greater complexity in
movement and function.
Question: What is radial symmetry?
Correct Answer: A body plan where body parts are arranged around a central axis.
Question: What is bilateral symmetry?
Correct Answer: A body plan where the left and right sides are mirror images of each other.
Question: What is the biological definition of an animal?
Correct Answer: All members of the kingdom Animalia (Metazoa), characterized as multicellular
eukaryotes that lack cell walls.
Question: How many known animal species exist on Earth?
Correct Answer: More than 1 million.
Question: What are the basic characteristics of animals?
Correct Answer: Multicellular, heterotrophic, motile at some life stage, reproduces sexually or asexually,
and most have nerves and muscles.
Question: What does it mean that the animal kingdom is monophyletic?
Correct Answer: All taxa evolved from a single common ancestor.
Question: How many recognized animal phyla are there?
Correct Answer: Approximately 35.
Question: What is the significance of clades in animal classification?
Correct Answer: Clades are monophyletic groups sharing a common ancestor based on shared
characteristics.
Question: What is the hypothesized evolutionary origin of animals?
Correct Answer: Evolved from a colonial unicellular ancestor, likely a flagellated protist.
Question: What is the developmental reorganization that leads to a two-layered animal?
Correct Answer: Formation of a sac-within-a-sac body plan (gastrula) with specialized feeding cells.
, Question: What role does the extracellular matrix play in animals?
Correct Answer: It provides tissue stability through cell junctions.
Question: What are the two main patterns of embryonic development?
Correct Answer: Protostomes (mouth forms first) and Deuterostomes (anus forms first).
Question: What is zygote cleavage?
Correct Answer: The rapid division of cells in the early embryo without significant growth, leading to a
morula and then a blastula.
Question: What distinguishes protostomes from deuterostomes in terms of cleavage?
Correct Answer: Protostomes exhibit spiral cleavage, while deuterostomes exhibit radial cleavage.
Question: What is gastrulation in embryonic development?
Correct Answer: The process where the blastula invaginates to form germ layers (ectoderm, mesoderm,
endoderm).
Question: What are the three germ layers formed during gastrulation?
Correct Answer: Ectoderm, mesoderm, and endoderm, which differentiate to form various tissues.
Question: What is the significance of cleavage patterns in animal lineages?
Correct Answer: They help distinguish between major lineages, affecting developmental pathways.
Question: What is a common method of asexual reproduction in animals?
Correct Answer: Budding in hydra, fragmentation in echinoderms, and parthenogenesis in some insects
and reptiles.
Question: What is the role of germ line cells in reproduction?
Correct Answer: They undergo meiosis to produce haploid gametes for sexual reproduction.
Question: What happens during fertilization in animal reproduction?
Correct Answer: Gametes fuse to form a diploid zygote.
Question: What is a morula?
Correct Answer: A compact mass of cells formed after zygote cleavage.
Question: What is a blastula?
Correct Answer: A hollow sphere of a single layer of cells unique to animals, derived from the morula.
Question: What is the significance of the blastula in animal development?
Correct Answer: It marks a key stage in embryonic development leading to further differentiation.
Question: What is the evolutionary significance of choanoflagellates?
Correct Answer: They are similar to modern colonial flagellated species, supporting the hypothesis of
animal evolution.
Question: What are the specialized functions of cells in early animal development?
Correct Answer: Certain cells become specialized for feeding and other functions during development.
Answers
Question: What is homeostasis?
Correct Answer: Regulation of the body's internal environment at or near a stable level.
Question: Why is homeostasis necessary?
Correct Answer: It allows organisms to maintain optimal physiological performance despite changes in
internal or external environments.
Question: What is the difference between regulators and conformers?
Correct Answer: Regulators maintain internal conditions regardless of external changes, while conformers
adjust their internal conditions to match external changes.
Question: What types of feedback are involved in homeostasis?
Correct Answer: Negative feedback, positive feedback, and feedforward.
Question: What is negative feedback?
Correct Answer: A mechanism that returns a variable toward a set point, minimizing the difference
between actual levels and the set point.
Question: How does negative feedback work in body temperature regulation?
Correct Answer: Endothermic animals use negative feedback to balance heat loss and gain, maintaining
body temperature near a set point.
Question: What is positive feedback?
Correct Answer: A mechanism that moves a variable away from the set point, amplifying the difference
until it is shut off by negative feedback.
Question: Give an example of positive feedback.
Correct Answer: Childbirth, where oxytocin stimulates labor.
Question: What is feedforward?
Correct Answer: A mechanism where future needs are anticipated and physiological adjustments are made
in advance.
Question: What is a fever?
Correct Answer: An elevated core body temperature as a defense response against pathogens, resulting
from a change in the internal set point.
Question: What happens during a fever?
Correct Answer: The hypothalamus raises the internal set point, activating the immune system to fight
infection.
Question: What are some variables regulated by homeostasis?
Correct Answer: Temperature, nutrients, oxygen, carbon dioxide, waste, water, salt, and pH.
Question: What is the goal of homeostasis?
,Correct Answer: To allow organisms to achieve optimal physiological performance.
Question: What is the difference between acoelomate, pseudocoelomate, and coelomate?
Correct Answer: Acoelomates lack a body cavity; pseudocoelomates have a fluid-filled cavity; coelomates
have a true body cavity lined with mesoderm.
Question: What are protostomes and deuterostomes?
Correct Answer: Protostomes develop the mouth first, while deuterostomes develop the anus first.
Question: What is cephalization?
Correct Answer: The concentration of sensory organs and nervous tissue at the anterior end of an
organism.
Question: What is segmentation?
Correct Answer: The division of the body into repetitive segments, allowing for greater complexity in
movement and function.
Question: What is radial symmetry?
Correct Answer: A body plan where body parts are arranged around a central axis.
Question: What is bilateral symmetry?
Correct Answer: A body plan where the left and right sides are mirror images of each other.
Question: What is the biological definition of an animal?
Correct Answer: All members of the kingdom Animalia (Metazoa), characterized as multicellular
eukaryotes that lack cell walls.
Question: How many known animal species exist on Earth?
Correct Answer: More than 1 million.
Question: What are the basic characteristics of animals?
Correct Answer: Multicellular, heterotrophic, motile at some life stage, reproduces sexually or asexually,
and most have nerves and muscles.
Question: What does it mean that the animal kingdom is monophyletic?
Correct Answer: All taxa evolved from a single common ancestor.
Question: How many recognized animal phyla are there?
Correct Answer: Approximately 35.
Question: What is the significance of clades in animal classification?
Correct Answer: Clades are monophyletic groups sharing a common ancestor based on shared
characteristics.
Question: What is the hypothesized evolutionary origin of animals?
Correct Answer: Evolved from a colonial unicellular ancestor, likely a flagellated protist.
Question: What is the developmental reorganization that leads to a two-layered animal?
Correct Answer: Formation of a sac-within-a-sac body plan (gastrula) with specialized feeding cells.
, Question: What role does the extracellular matrix play in animals?
Correct Answer: It provides tissue stability through cell junctions.
Question: What are the two main patterns of embryonic development?
Correct Answer: Protostomes (mouth forms first) and Deuterostomes (anus forms first).
Question: What is zygote cleavage?
Correct Answer: The rapid division of cells in the early embryo without significant growth, leading to a
morula and then a blastula.
Question: What distinguishes protostomes from deuterostomes in terms of cleavage?
Correct Answer: Protostomes exhibit spiral cleavage, while deuterostomes exhibit radial cleavage.
Question: What is gastrulation in embryonic development?
Correct Answer: The process where the blastula invaginates to form germ layers (ectoderm, mesoderm,
endoderm).
Question: What are the three germ layers formed during gastrulation?
Correct Answer: Ectoderm, mesoderm, and endoderm, which differentiate to form various tissues.
Question: What is the significance of cleavage patterns in animal lineages?
Correct Answer: They help distinguish between major lineages, affecting developmental pathways.
Question: What is a common method of asexual reproduction in animals?
Correct Answer: Budding in hydra, fragmentation in echinoderms, and parthenogenesis in some insects
and reptiles.
Question: What is the role of germ line cells in reproduction?
Correct Answer: They undergo meiosis to produce haploid gametes for sexual reproduction.
Question: What happens during fertilization in animal reproduction?
Correct Answer: Gametes fuse to form a diploid zygote.
Question: What is a morula?
Correct Answer: A compact mass of cells formed after zygote cleavage.
Question: What is a blastula?
Correct Answer: A hollow sphere of a single layer of cells unique to animals, derived from the morula.
Question: What is the significance of the blastula in animal development?
Correct Answer: It marks a key stage in embryonic development leading to further differentiation.
Question: What is the evolutionary significance of choanoflagellates?
Correct Answer: They are similar to modern colonial flagellated species, supporting the hypothesis of
animal evolution.
Question: What are the specialized functions of cells in early animal development?
Correct Answer: Certain cells become specialized for feeding and other functions during development.
