AcaDeca: Science Flashcards ('26-'27)

Based upon AcaDeca Science Resource Guide from 2026-2027. Created by Veda Bharath.

Animal

A living organism that feeds on organic matter, is able to move from one place to another, and is composed of multiple eukaryotic cells that produce collagen.

Collagen

A protein found in skin, tendons, bones, and ligaments that provides structure to animal cells and holds them together.

Eukaryotic cells

Cells characterized by internal components separated by membranes, called organelles, which play specific roles in maintaining the life of the cell.

Mammals

Animals that have spinal cords and brains, produce milk via mammary glands, possess hair, and have three middle ear bones.

Viviparous

A term describing animals that give birth to live young.

Monotremes

Mammals that reproduce by laying eggs, such as the platypus ($Ornithorhynchus\,anatinus$) and echidna ($Tachyglossidae$).

Oviparous

A term describing animals that reproduce by laying eggs.

Ovoviviparous

A term describing animals that give live birth to offspring that developed and hatched internally in eggs.

Arthropods

A group including insects and arachnids that lack a spinal cord, have an open circulatory system using hemolymph, and are supported by an exoskeleton.

Behavior

In a broad sense, all the ways animals interact with other organisms, internal signals, and the physical environment.

Internal stimuli

Sensations that come from within an organism’s own body, such as signals triggering shivering when cold.

External stimuli

Anything outside of the animal to which it can react or respond, such as a cat seeing a mouse.

Ecology

The study of how living organisms interact with their environment to maximize their chances of survival and reproduction.

Keystone species

An animal species vital to an ecosystem whose removal would cause the system to collapse.

Taxonomy

The field of research concerned with the classification of all organisms using a standardized series of names from broad to specific.

Phylogenetic trees

Visual descriptions of the evolutionary history between taxa based on biological features, behavior, genetics, or geographic location.

Divergence event

The point on an evolutionary tree where two species can no longer breed with one another because their genetic code has become too different.

Last Universal Common Ancestor (LUCA)

The theoretical single-celled ancestor organism believed to have lived over $4.2$ billion years ago from which all life formed.

Pneumodesmus newmani (P. newmani)

A millipede-like insect creature that lived approximately $420$ million years ago; the first known animal to breathe oxygen and walk on land.

Evolution

The total change in a population of organisms over time, applying to both physical and behavioral traits.

Fitness

The measure of how well an individual is suited for its environment and its level of success at surviving and reproducing.

Natural selection

A mechanism formulated by Charles Darwin that drives evolution by acting on the physical manifestation of traits in individuals.

Kin selection

The theory that self-sacrificing behavior persists because it increases the fitness of genetically related relatives carrying similar genetic code.

Ethology

The scientific study of animal behavior.

Imprinting

A process discovered by Konrad Lorenz where young animals, during a critical point in development, recognize specific stimuli as a parent.

Tinbergen’s Four Questions

A theoretical framework for describing behavior based on function (adaptation), history (evolution), cause (mechanism), and development (ontogeny).

Anthropomorphism

The bias of viewing the behavior of animals through the lens of human behavior and emotions.

Ethogram

A standardized tool using detailed written descriptions of behavior to quantify the frequency or types of behavior exhibited.

Inter-rater reliability

A measure of accuracy where the results of two or more researchers are compared to ensure behaviors are consistently identified.

Nervous system

A complex system of tissues used by animals to respond to their internal and external environment through behavior.

Neurons

Individual cells that make up the nervous system and are responsible for the transmission of electrical impulses.

Sensation

The physical detection of stimuli, such as touch or smell, through sensory cells.

Perception

The process of converting sensations into interpreted information based on an individual's memory, learning, and emotions.

Nociceptors

Specialized pain receptors that detect pressure and temperature to protect an animal from harm.

Reflexes

Behaviors that occur instantaneously without the message traveling to the brain, such as pulling away from a hot object.

Proprioception

The internal sense that helps the brain determine where the body and its limbs are located in space.

Sympathetic nervous system

The "fight or flight" system of the autonomic nervous system that prepares the body for conflict or survival by increasing heart rate and respiration.

Parasympathetic nervous system

The "rest and digest" system that acts to return the animal's body to a state of balance and relaxation after danger has passed.

Blood-brain barrier

A selective layer of cells surrounding the brain's blood supply that protects the organ from bacteria and viruses.

Hormones

Chemical signaling molecules released by endocrine glands that travel through the bloodstream to target tissues.

Endogenous hormones

Hormones created within the body of an organism.

Exogenous hormones

Hormones obtained from outside the body, such as through food or medications.

Homeostasis

The optimal internal conditions needed to maintain life, which animals seek to stabilize via behavior.

HPA axis

The hypothalamic-pituitary-adrenal axis, a negative feedback loop using cortisol to regulate an animal's response to stress.

Chronobiology

The study of biological rhythms, or the internal mechanisms that allow animals to detect the passage of time.

Circadian rhythms

Biological rhythms that repeat approximately every $24$ hours and persist even in the absence of external cues.

Suprachiasmatic nucleus (SCN)

A small part of the midbrain in vertebrates that acts as the master timekeeper for biological rhythms.

Zeitgeber

An external cue, such as daylight, used by an animal to regulate or reset its biological clock.

Diurnal

Animals that are primarily awake during the day and asleep at night.

Nocturnal

Animals that are primarily awake at night and asleep during the day.

Crepuscular

Animals that are primarily active during the transition periods of dawn and dusk.

Fixed-motor pattern

An instinctual behavior that occurs the same way every time a specific stimulus is presented, regardless of environmental changes.

Habituation

A form of nonassociative learning where an animal decreases its response to a non-threatening stimulus over repeated exposure.

Sensitization

A form of nonassociative learning where a repeated important or dangerous stimulus causes an increase in reaction over time.

Synaptic plasticity

The ability of an animal’s neuronal connections to change or strengthen over time based on experience, serving as the foundation of learning.

Classical conditioning

A form of associative learning where a neutral stimulus is paired with an unconditioned stimulus until the neutral stimulus alone elicits a response.

Operant conditioning

A form of associative learning where an animal learns that a specific voluntary behavior will result in a specific outcome or reward.

Spatial cognition

The ability of an animal to orient itself in space using landmarks, memorized routes, and mental cognitive maps.

Social learning

A complex form of learning that occurs when animals observe other individuals and modify their own behavior based on those observations.

Epigenetic modification

Changes in gene expression brought on by environmental factors or behavior that do not directly modify the DNA sequence.

Diet

A constant set of food types that an individual of a species is capable of eating to fulfill its nutritional and energy needs.

Generalists

Resourceful animals adapted to a broad ecological niche that can eat a variety of foods and adapt to different environments.

Specialists

Animals adapted to a very narrow ecological niche or a specific food source, making them vulnerable to rapid environmental changes.

Optimal foraging theory

A mathematical model suggesting animals maximize fitness by obtaining the highest amount of energy from food while using the least amount of energy to get it.

Evolutionary game theory

A foraging theory describing interactions between strategies (e.g., Hawk vs. Dove) where the optimal solution depends on how a rival responds.

Signal

An intentional, honest, and reliable behavior that conveys specific information to benefit both the sender and the receiver.

Cue

A guide for behavior that benefits only the receiver and is not necessarily an intentional message from the sender.

Cultural transmission

A subset of social learning where shared behaviors are intentionally or unintentionally passed between generations within a specific group.

Sexual selection

The evolutionary process where traits or behaviors are changed due to the preference of one sex, typically females.

Sexual dimorphism

The condition where the males and females of a species exhibit significant physical differences in size, color, or shape.

Runaway selection

A theory suggesting that preferred traits become increasingly exaggerated over time because they signal high fitness to a mate.

Anti-predatory behavior

The behaviors animals engage in to avoid being detected, chased, or eaten by predators.

Eusocial

The highest level of social organization, featuring a caste system, shared offspring care, and multiple generations living together.

Social monogamy

A mating system where a pair stays together in a communal home and raises young but may occasionally engage in extra-pair matings.

Affective state

A long-lasting emotional state in an animal based on prior experiences rather than a single immediate stimulus.

Arousal

The intensity of an emotional state, ranging from low (boredom) to high (anger).

Valence

The measure of how pleasant or unpleasant an emotional experience is for an individual.

Domestication

A long-term process of selectively breeding animals over hundreds of generations to live within and benefit human society.

Neoteny

The retention of juvenile physical and behavioral traits in adult domesticated animals compared to their wild ancestors.

HIREC

Human-Induced Rapid Environmental Change, describing accelerated environmental shifts caused by humans that outpace animal evolution.

Migration

The act of animals moving from one region to another as part of their life cycle or as an annual act that eventually returns them to their start.

Zugunruhe

A German word describing the restlessness migratory animals experience when their internal biological clock indicates it is time to move.

Obligate migrators

Animals that must migrate as a requirement of their life cycle or to survive.

Facultative migrators

Animals that can choose whether to migrate or not based on local resource availability and conditions.

Magnetoreception

The ability of certain animals to detect and use the Earth’s magnetic field for navigation.

Quorum response

A group decision-making process where the probability of an individual behaving in a way increases as more individuals in the group do so.

Diel vertical migration (DVM)

The daily movement of marine organisms from deep water to the ocean surface at night to feed while avoiding predators.

Biological carbon pump

The process by which organisms involved in DVM trap carbon from the surface deep underwater when they die or return to the depths.

Invasive species

Non-native species transplanted by human activity that outcompete native wildlife and disrupt local ecosystems.