Unit 3: Animal Biology and Ecology Summary

33.1 Animal Body Parts
Porifera: Sponges; characterized by few types of cells, which include choanocytes for filter feeding, and a simple body structure with no well-defined tissues. They display no symmetry and have a porous body that allows water to flow through, facilitating nutrient absorption and waste removal.

Cnidaria: Includes jellyfish and sea anemones; features radial symmetry, allowing them to interact with their environment from all sides. They possess two germ layers (ectoderm and endoderm) and an internal gastrovascular cavity that serves as both a digestive and circulatory system. Cnidarians are known for their specialized cells called cnidocytes, which contain nematocysts that capture prey.

Bilateria: Animals displaying bilateral symmetry, which allows for a distinct head and tail (anterior and posterior) and the development of a centralized nervous system. This group is divided into two major clades: Protostomes and Deuterostomes.

Cephalization: Refers to the concentration of sensory and nervous system components at one end of the body, leading to the development of a head region. This trait enhances an organism's ability to interact with the environment effectively.

Segmentation: The division of the body into discrete segments, which allows for more complex movements and the specialization of body parts. This is seen in organisms like annelids (segmented worms) and arthropods.

Diploblastic: Refers to organisms with two germ layers (endoderm and ectoderm). This structural simplicity limits the complexity of the organisms.

Triploblastic: Organisms that develop three germ layers (ectoderm, endoderm, and mesoderm), allowing for the development of more complex organs and systems.

Protostomes: A group where the blastopore, the first opening that forms during embryonic development, becomes the mouth. This includes diverse phyla such as mollusks and arthropods, which exhibit a variety of body plans and adaptations.

Deuterostomes: In contrast to protostomes, here the blastopore develops into the anus, with a second opening forming the mouth. This clade includes chordates, which possess a notochord during some stage of development, leading to the evolution of vertebrates, including humans.

33.2 Tissues and Organs
Tissues: Defined as a collection of cells that work together to perform a specific function. The four primary tissue types are epithelial (protective coverage and secretion), connective (supporting and binding tissues), muscle (facilitating movement), and nervous (transmitting signals).

Organs: Formed from combinations of two or more tissue types working collaboratively to achieve a specific function within an organism, such as the heart (muscle and connective tissue) or skin (epithelial and connective tissue).

33.3 Homeostasis
Homeostasis: Encompasses the regulatory processes that maintain a stable internal environment, essential for the survival of living organisms. Mechanisms include temperature regulation, pH balance, and electrolyte levels.

Negative Feedback: A critical mechanism where the output of a process opposes the initial stimulus, promoting the maintenance of steady internal conditions. Example: when body temperature rises, mechanisms are activated to dissipate heat.

Set Point: The target level or range of a physiological variable maintained by homeostasis. For instance, the human body maintains an average temperature of about 37°C.

33.4 Evolutionary History
Cambrian Explosion: Refers to a significant event approximately 541 million years ago marked by an unprecedented increase in the diversity and complexity of life forms, leading to the establishment of many major animal phyla that still exist today.

Mass Extinction: Periods in Earth’s history characterized by a rapid reduction in biodiversity due to catastrophic events, such as volcanic eruptions or asteroid impacts, which have repeatedly altered the course of evolutionary history.

34.1 Animal Diversity
The evolution of animals encompasses a broad array of lineages, including sponges, cnidarians, and bilaterians, each contributing to the complexities of ecological interactions.

Eumetazoa: A clade of animals that possess true tissues and undergo gastrulation, which leads to more complex body structures compared to organizations like Porifera.

34.2 Protostome Animals
Protostomia: Referring to animals where the blastopore develops into the mouth, showcasing a diverse evolutionary pathway with adaptations to various ecological niches.

Ecdysozoa: A subgroup of Protostomia that is characterized by the process of molting their exoskeleton, which allows for growth. This group includes arthropods and nematodes.

Lophotrochozoa: Another subgroup of Protostomia, known for having a lophophore or a trochophore larval stage, which includes diverse groups such as mollusks (e.g., snails and clams) and annelid worms (e.g., earthworms and leeches).

34.3 Arthropods
Chitin: A polysaccharide that forms the exoskeletons of arthropods, providing structural support and protection. This adaptation is crucial for terrestrial survival as it reduces water loss.

Major groups of arthropods include insects (the most diverse group), chelicerates (e.g., spiders, scorpions), myriapods (e.g., centipedes, millipedes), and crustaceans (e.g., crabs, lobsters).

34.4 Deuterostome Animals
Chordata: A diverse phylum that includes vertebrates, characterized by the presence of a notochord, a dorsal hollow nerve cord, and pharyngeal slits at some stage of development. This group is vital for the study of complex organisms, including humans and other mammals.

43.1 Tinbergen's Questions
Understanding animal behaviors necessitates exploring innate (instinctive) behaviors and learned behaviors (acquired through experience), leading to insights into the evolution of social structures and interactions.

43.2 Dissecting Behavior
Displays: Internal and external behavioral outputs, including fixed action patterns (FAPs) which are instinctual responses that follow a specific sequence upon a trigger stimulus, illustrating the importance of stimulus-response evolution.

44.1 Populations and Their Properties
Population: a group of individuals of the same species that occupy a defined geographical area and share genetic similarities. Understanding population dynamics is crucial in ecology.

Density: Refers to the number of individuals per unit area, which can influence interactions such as competition, availability of resources, and overall population health.

44.2 Population Growth and Decline
Factors influencing population dynamics include immigration, emigration, birth, and death rates, which all impact the size and stability of populations.
Exponential Growth: Occurs when the per capita growth rate remains constant, resulting in rapid population increases under ideal conditions, following a J-shaped curve.

45.1 The Niche
Niche: The ecological role of a species in its environment, defined by both abiotic (non-living) factors like climate and biotic (living) factors such as interactions with other species. Exploring niches helps understand ecosystem dynamics and interspecies relationships.