Animal characteristics, classification and symmetry

• Animals are multicellular, eukaryotic organisms belonging to the kingdom Animalia.

Animal Characteristics

• Animals are heterotrophic; they obtain energy by consuming other organisms.
• Animals are multicellular with specialized cells and lack cell walls.
• Animals typically reproduce sexually and have a nervous system, except for sponges.

Classification of Animals

• Vertebrates possess a backbone, examples are fish, amphibians, reptiles, birds, and mammals.
• Invertebrates lack a backbone and examples sponges, cnidarians, mollusks, and arthropods.

Symmetry in Animals

• Asymmetry means no symmetry, such as in sponges.
• Radial symmetry is symmetry around a central axis like jellyfish and starfish.
• Bilateral symmetry is divided into equal halves like humans, insects, and fish.

Levels of Organization in Animals

• In the cellular level, sponges (Porifera) are an example.
• In the tissue level, cnidarians (jellyfish, corals) are an example.
• In the organ level, flatworms (Platyhelminthes) are an example.
• In the organ system level, vertebrates (humans, mammals) are an example.

Animal Tissues

• Epithelial tissue covers body surfaces and functions in protection, secretion, and absorption.
• Connective tissue supports, connects, and protects, for example, blood, bone, cartilage, and fat.
• Muscle tissue enables movement, with types including skeletal, smooth, and cardiac.
• Nervous tissue sends electrical signals, composed of neurons and glial cells.

Animal Body Plans

• Acoelomates lack a body cavity, for example, flatworms.
• Pseudocoelomates have a false body cavity, for example, roundworms.
• Coelomates possess a true body cavity, for example, annelids, mollusks, arthropods, and chordates.
• Segmentation is repeated body segments found in annelids, arthropods, and vertebrates.
• Cephalization is the concentration of sensory organs in the head, for example, insects and mammals.

Modes of Nutrition in Animals

• Herbivores eat plants; examples are cows and rabbits.
• Carnivores eat meat; examples are lions and hawks.
• Omnivores eat both plants and animals; examples are humans and bears.
• Detritivores eat decaying organic matter; examples are earthworms and some insects.
• Filter feeders strain food particles from water, such as sponges and whales.
• Parasites live and feed on a host, such as tapeworms and lice.

Animal Reproduction and Development

• Budding is when outgrowth of a part of a cell or body region leads to a separation from the original organism into two individuals, such as hydra.
• Fragmentation is when the parent breaks off and develops into an entirely new but genetically identical individual; an example is starfish regeneration.
• Parthenogenesis is where the offspring of some species develops from the egg or female gamete without first being fertilized by the male gamete, which occurs in some insects and lizards.
• Sexual reproduction involves fertilization, which can be external or internal.
• Oviparous development is when eggs hatch outside the body, for example, birds and frogs.
• Ovoviviparous development is when eggs develop inside, then hatch internally, for example, some sharks.
• Viviparous development is live birth with nourishment from the mother, for example, humans and dogs.

Animal Adaptations

• Structural adaptations are physical features, such as camouflaged fur and sharp claws.
• Behavioral adaptations are actions, such as migration and hibernation.
• Physiological adaptations are internal body functions, such as venom production and temperature regulation.

Importance of Animals in Ecosystems

• Pollination is an important role performed by bees and butterflies.
• Decomposition is carried out by fungi and worms.
• Predator-prey relationships maintain balance in ecosystems.
• Animals serve as a food source for both humans and other animals.

Introduction to Body Systems

• The human body is composed of multiple organ systems that maintain homeostasis.
• Body systems in both invertebrates and vertebrates (humans) are discussed.

The 11 Human Body Systems and Their Functions

• The integumentary system protects the body, regulates temperature, and prevents dehydration.
• The muscular system enables movement, posture, and heat production.
• The skeletal system provides structure, support, and protection for organs and enables movement.
• The nervous system controls body functions and responds to stimuli.
• The circulatory system transports nutrients, oxygen, and waste products.
• The respiratory system facilitates gas exchange (oxygen in, carbon dioxide out).
• The digestive system breaks down food for nutrient absorption and energy production.
• The excretory system removes waste and maintains fluid and electrolyte balance.
• The reproductive system enables reproduction and production of offspring.
• The endocrine system regulates hormones and body processes.
• The lymphatic/immune system defends the body against infections and diseases.

Respiratory System (Gas Exchange/Respiration)

• The respiratory system allows oxygen intake and carbon dioxide removal.
• Major organs include the nasal cavity (humidifies, purifies, moistens, warms, and filters the air), larynx (voice box and passageway for air), trachea (windpipe), bronchi, bronchioles and alveoli (the functional unit where gas exchange occurs).

Circulatory System (Blood Circulation)

• The circulatory system transports oxygen, nutrients, and hormones while removing waste products.
• In a closed circulatory system, blood is pumped through arteries, veins, and capillaries. Oxygen is carried by hemoglobin.
• In an open circulatory system, blood leaves the vessel and seeps through spaces, then moves back into a vein.

Types of Circulation in Humans

• Pulmonary circulation occurs when blood flows to the lungs for oxygenation.
• Coronary circulation supplies blood to the heart itself.
• Renal circulation: Blood flows to the kidneys.
• Hepatic circulation is where blood flows to the liver.

Pathway of Blood During Circulation

• Blood enters the right atrium via the vena cava, passes through the tricuspid valve into the right ventricle, and pumps through the pulmonary artery to the lungs.
• Oxygenated blood returns via the pulmonary vein to the left atrium, flows through the bicuspid valve into the left ventricle, and pumps through the aorta to supply oxygenated blood to the body.
• Blood entering the right side of the heart is unoxygenated, and blood entering the left side of the heart is oxygenated.
• Valves prevent backflow and ensure one-way blood flow.

Excretory System (Waste Removal & Balance Maintenance)

• Removes waste and maintains the body's fluid and electrolyte balance.

Examples of Excretory Structures in Invertebrates

• Flame cells are found in flatworms.
• Nephridia are found in annelids.
• Malpighian tubules are found in insects.
• Green glands are found in crustaceans.

Digestive System (Nutrition & Energy)

• Converts food into usable energy through digestion and nutrient absorption.

Specialized Structures in Some Animals

• Crops store food temporarily, such as in birds and earthworms.
• Gizzards grind food, such as in birds and annelids.

Body Systems Working Together

• Organ systems interact to maintain homeostasis (internal balance).
• The respiratory system provides oxygen to the circulatory system, which transports it to muscles controlled by the nervous system.

Introduction to Mendelian Genetics

• Mendelian Genetics refers to the principles of heredity established by Gregor Mendel and his experiments on pea plants.
• Key focus is how traits are inherited, understanding dominant and recessive traits, and the role of alleles in genetic inheritance.
• Gregor Mendel (1822–1884) was an Austrian monk who conducted experiments on pea plants to understand heredity, leading to the formulation of the Laws of Inheritance.
• He studied seven traits of pea plants: seed shape, seed color, pod shape, pod color, flower color, flower position, and plant height.

Mendel's Laws of Inheritance

• Each individual has two alleles for each trait, one inherited from each parent.
• During gamete formation, these alleles separate, ensuring that each gamete carries only one allele for each trait.
• Genes for different traits are inherited independently of each other; the inheritance of one trait does not affect the inheritance of another.
• When two different alleles are present, one is dominant (expressed), while the other is recessive.

Important Genetic Terms

• Gene: A segment of DNA that determines a trait.
• Allele: A variant of a gene (e.g., dominant allele ‘A' and recessive allele 'a').
• Homozygous: Having two identical alleles (AA or aa).
• Heterozygous: Having two different alleles (Aa).
• Genotype: The genetic makeup of an organism (e.g., AA, Aa, or aa).
• Phenotype: The physical expression of a trait (e.g., purple flowers, tall plants).
• Dominant Trait: A trait expressed even when only one copy of the allele is present (e.g., 'A' in Aa or AA).
• Recessive Trait: A trait only expressed when two recessive alleles are present (aa).

Punnett Squares and Predicting Inheritance

• Punnett Square: A diagram used to predict the possible genotypes and phenotypes of offspring.
• Monohybrid Cross: A genetic cross involving one trait, crossing two heterozygous tall plants result in possible offspring such as 75% Tall, and 25% short.
• Dihybrid Cross: A genetic cross involving two traits result ratio of traits following a 9:3:3:1 pattern in F2 generation.

Applications of Mendelian Genetics

• Only one dominant allele is needed to express the disorder
• Two recessive alleles are required for a recessive disorder to occur
• Selective: Using Mendelian principles to breed plants and animals for desirable traits.
• Genetic: Identifying carriers of genetic diseases.