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Questions and Answers
Which key trait distinguishes animals from other life forms?
Which key trait distinguishes animals from other life forms?
What significant event in animal evolution began around 550 million years ago?
What significant event in animal evolution began around 550 million years ago?
Which of the following options is NOT a trait shared by animals?
Which of the following options is NOT a trait shared by animals?
What do nerve cells called neurons do in animals?
What do nerve cells called neurons do in animals?
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How do most animals obtain their necessary carbon compounds?
How do most animals obtain their necessary carbon compounds?
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What is the estimated range of extant animal species?
What is the estimated range of extant animal species?
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Which group of animals are noted for lacking nerve cells?
Which group of animals are noted for lacking nerve cells?
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What term refers to the structural framework found outside cells in animals?
What term refers to the structural framework found outside cells in animals?
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Which type of limbs is characterized by having segments that can bend freely?
Which type of limbs is characterized by having segments that can bend freely?
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Which reproductive strategy involves the fusion of gametes outside of the female organism?
Which reproductive strategy involves the fusion of gametes outside of the female organism?
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Which type of cell division is involved in asexual reproduction?
Which type of cell division is involved in asexual reproduction?
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Which of the following are considered specialized sensory abilities in some animals?
Which of the following are considered specialized sensory abilities in some animals?
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What is a significant characteristic of diploid-dominant life cycles in animals?
What is a significant characteristic of diploid-dominant life cycles in animals?
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Which of the following describes the process of metamorphosis?
Which of the following describes the process of metamorphosis?
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What type of feeders primarily consume organic material from the seafloor?
What type of feeders primarily consume organic material from the seafloor?
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Which structure is primarily used by echinoderms for locomotion?
Which structure is primarily used by echinoderms for locomotion?
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Which of the following correctly defines detritivores?
Which of the following correctly defines detritivores?
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Which sensory ability allows some birds to detect changes in weather conditions?
Which sensory ability allows some birds to detect changes in weather conditions?
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Which type of fertilization occurs within the female's body?
Which type of fertilization occurs within the female's body?
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What sensory ability is notably used by some aquatic predators in hunting?
What sensory ability is notably used by some aquatic predators in hunting?
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What distinguishes viviparous organisms in their reproductive process?
What distinguishes viviparous organisms in their reproductive process?
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Which group of animals primarily consumes plant-based material?
Which group of animals primarily consumes plant-based material?
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What type of feeding strategy involves consuming both plant and animal material?
What type of feeding strategy involves consuming both plant and animal material?
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Which of the following is a method by which animals can feed on particles suspended in water?
Which of the following is a method by which animals can feed on particles suspended in water?
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What type of symmetry do bilaterians exhibit?
What type of symmetry do bilaterians exhibit?
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Which type of genes is responsible for regulating the anterior–posterior axis in bilaterians?
Which type of genes is responsible for regulating the anterior–posterior axis in bilaterians?
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What is the significance of cephalization in bilaterians?
What is the significance of cephalization in bilaterians?
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The coelom is important because it serves which of the following functions?
The coelom is important because it serves which of the following functions?
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Which statement accurately describes the relationship between the nervous system and bilateral symmetry?
Which statement accurately describes the relationship between the nervous system and bilateral symmetry?
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What is the role of the cerebral ganglion or brain in bilaterians?
What is the role of the cerebral ganglion or brain in bilaterians?
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Which germ layer gives rise to the skin and nervous system in bilaterians?
Which germ layer gives rise to the skin and nervous system in bilaterians?
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The basic bilaterian body shape is best described as:
The basic bilaterian body shape is best described as:
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What primary function does the coelom serve in bilaterally symmetric organisms?
What primary function does the coelom serve in bilaterally symmetric organisms?
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In which subgroup does the mouth develop before the anus during embryonic development?
In which subgroup does the mouth develop before the anus during embryonic development?
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Which of the following groups includes organisms that develop their coelom by hollowing out blocks of mesoderm?
Which of the following groups includes organisms that develop their coelom by hollowing out blocks of mesoderm?
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What defines the group known as Lophotrochozoa?
What defines the group known as Lophotrochozoa?
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Which statement accurately describes segmentation in vertebrates?
Which statement accurately describes segmentation in vertebrates?
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What common feature is attributed to both annelids and arthropods related to segmentation?
What common feature is attributed to both annelids and arthropods related to segmentation?
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Which characteristic distinguishes Ecdysozoa from Lophotrochozoa?
Which characteristic distinguishes Ecdysozoa from Lophotrochozoa?
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Which of the following is NOT a sensory organ category highlighted in the differentiation themes?
Which of the following is NOT a sensory organ category highlighted in the differentiation themes?
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What does it mean when animals are described as a monophyletic group?
What does it mean when animals are described as a monophyletic group?
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Which animal lineage is considered the most basal among the phylum Porifera?
Which animal lineage is considered the most basal among the phylum Porifera?
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From which type of organism is it believed that multicellularity originated?
From which type of organism is it believed that multicellularity originated?
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Which characteristic is associated with the lophotrochozoan group?
Which characteristic is associated with the lophotrochozoan group?
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What structure is indicative of the triploblastic organisms?
What structure is indicative of the triploblastic organisms?
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Which of the following is NOT a characteristic of protostomes?
Which of the following is NOT a characteristic of protostomes?
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Which group does the phylum Cnidaria include?
Which group does the phylum Cnidaria include?
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Which organisms are included in the Deuterostome group?
Which organisms are included in the Deuterostome group?
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What type of development do protostomes exhibit?
What type of development do protostomes exhibit?
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Which of the following represents a characteristic of the Ecdysis group?
Which of the following represents a characteristic of the Ecdysis group?
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Identify a feature unique to choanoflagellates that links them to animals.
Identify a feature unique to choanoflagellates that links them to animals.
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Which of the following is associated with the coelomate condition?
Which of the following is associated with the coelomate condition?
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Which organism is an example of a triploblastic animal?
Which organism is an example of a triploblastic animal?
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Study Notes
Biological Science - Introduction to Animals
- Animal phyla originated suddenly in the Cambrian period and diversified.
- The radiation of animals began around 550 million years ago during the Cambrian explosion.
- Biologists estimate between 8 million and 50 million extant animal species.
- Ancestors to animals were single-celled protists.
What is an Animal?
- Animals are eukaryotes with key traits:
- Multicellularity: Cells lack cell walls but have an extensive extracellular matrix.
- Heterotrophy: Obtain carbon compounds from other organisms, mostly by ingesting food.
- Motility: Move under their own power at some point in their life cycle.
- Animals (except sponges) have:
- Neurons: Transmit electrical signals.
- Muscle cells: Change body shape.
- Nervous system: Interconnected neurons. Muscle cells connect to neurons.
- Adaptions allow a large multicellular body to move efficiently.
33.2 Key Innovations
- Scientists study evolution through fossils, morphology, and molecular (genes) evidence.
- Key innovations: Multicellularity, embryonic tissue layers, bilateral symmetry, cephalization, and the nervous system, the coelom, protostomes vs. deuterostomes, segmentation are shown to be important in animal evolution.
Origin of Multicellularity
- Animals are a monophyletic group (single common ancestor).
- Sponges (phylum Porifera) are two of the most basal animal lineages.
- Multicellularity likely originated in a sponge-like animal.
Origin of Embryonic Tissue Layers
- Sponges have the tools for cell-cell and cell-ECM adhesion, but not complex tissues.
- Tissues are organized similar cells into functional units.
- Triploblasts are divided into two groups based on the embryonic tissue layers:
- Diploblasts have two germ layers (ectoderm and endoderm) - Triploblasts have three germ layers (ectoderm, endoderm, and mesoderm).
Origin & Diversification of Tissues
- Germ layers develop into adult tissues and organs.
- In triploblasts:
- Ectoderm develops into skin and nervous system.
- Endoderm develops into digestive tract lining.
- Mesoderm develops into circulatory system, muscles, bone, and other internal organs.
- Ectoderm produces the outer covering of the animal.
- Most cnidarians (jellyfish, corals, etc.) and ctenophores are diploblastic.
- All other animals are triploblastic.
- Mesoderm evolution led to complex muscles for movement.
Origin of Bilateral Symmetry, Cephalization, & the Nervous System
- Body symmetry (radial or bilateral) is a key morphological aspect of an animal's body plan.
- Cnidarians, ctenophores, and some sponges usually have radial symmetry.
- Other animals exhibit bilateral symmetry with a single plane of symmetry.
Homology or Convergent Evolution?
- Bilaterians are triploblastic, bilaterally symmetrical animals.
- Symmetry in bilaterians is due to Hox genes (anterior-posterior axis) and Decapentaplegic (dpp) genes (dorsal-ventral axis).
Origin of the Nervous System
- Evolution of the head and nervous system is linked to bilateral symmetry.
- Nervous systems can be nerve nets (diffuse neurons) or central nervous systems (neurons in clusters).
- The central nervous system (CNS) evolved along with cephalization (head).
- Large masses of neurons called ganglia or brain are in the head involved in brain function.
Origin of the Coelom
- The basic body shape of bilaterians is a tube within a tube.
- A coelom is an enclosed fluid-filled cavity between the tubes.
- It provides space for oxygen and nutrient circulation, allowing internal organs to move independently.
- A coelom likely evolved from the common ancestor of protostomes and deuterostomes.
Origin of Protostomes and Deuterostomes
- Bilaterally symmetrical animals with CNS, cephalization, and a coelom gave rise to diverse lineages.
- Two subgroups are based on embryonic development: protostomes and deuterostomes.
- Protostomes: Develop a mouth before the anus, mesoderm forms a coelom by hollowing out solid masses.
- Deuterostomes: Develop an anus before the mouth. Coelom originates from pockets pinching off of the gut.
Origin of Segmentation
- Segmentation is repeated body structures.
- A segmented backbone is a defining characteristic of vertebrates (fish, reptiles, birds, amphibians, and mammals).
- Invertebrates (animals without a backbone) also have segmentation (e.g., annelids and arthropods).
- Segmentation evolved independently.
Sensory Organs
- Sensory organs evolved with diversification and specialize.
- Sight
- Hearing
- Taste/Smell
- Touch
Specialized Sensory Abilities
- As animals diversified, more specialized sensory abilities evolved:
- Magnetic field detection
- Electric field detection
- Barometric pressure sensing
Diversification Themes - Ecological Roles
- Detritivores: Feed on dead organic matter (e.g., millipedes).
- Herbivores: Feed on plants or algae (e.g., pandas).
- Carnivores: Feed on animals (e.g., owls).
- Omnivores: Feed on both plants and animals (e.g., humans).
Diversification Themes - Feeding Strategies
- Suspension feeders: Capture food by filtering out particles from water or air (e.g., barnacles).
- Deposit feeders: Ingest organic material in a substrate (e.g., sea cucumbers).
- Fluid feeders: Suck or mop up liquids (e.g., butterflies).
- Mass feeders: Take chunks of food into their mouth (e.g., lions).
Diversification Themes - Movement
- Lobe-like limbs (e.g., onychophorans)
- Jointed limbs (e.g., arthropods such as crabs)
- Parapodia (segmented worms)
- Tube feet (e.g., sea stars)
- Tentacles (e.g., octopuses), various adaptations for movement and other functions in animal life.
Diversification Themes - Reproduction
- Asexual reproduction involves cell division.
- Sexual reproduction:
- External fertilization: Eggs and sperm released into water.
- Internal fertilization: Fertilization inside the female's body.
- Embryo development modes: Viviparous (nourishes embryos internally), Oviparous (fertilized eggs deposit to outside for hatching), Ovoviviparous (eggs retained internally).
Life Cycles
- Most sexually reproducing animals have diploid-dominant life cycles (haploid gametes are short lived).
- Exceptions exist, including metamorphosis (dramatic change).
- Direct: Develop from one stage to another without change.
- Indirect: Development involves a larval stage followed by metamorphosis.
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Description
Test your knowledge on key traits and evolutionary milestones in the animal kingdom. This quiz covers essential topics ranging from cell structures to reproductive strategies. Perfect for students studying animal biology or those interested in evolution.
