Introduction to Genetics

• Genetics is a branch of science that studies DNA, genes, genetic variation, and heredity in living organisms.

Reproductive Cells and Chromosomes

• Reproductive cells contain 23 chromosomes.
• An organism maintains the same chromosomes and gene set throughout its life.
• Chromosomes are located within the nucleus of cells.
• Chromosomes are made of Deoxyribonucleic Acid (DNA) that contains genes.

Heredity and Variation

• Heredity is the passing of traits or characteristics through genes from parent to offspring.
• Variation refers to the naturally occurring genetic differences among individuals of the same species.
• Variation allows for flexibility and survival within a population facing environmental changes, facilitating adaptation.
• Genes are the reason offspring resemble their parents.

Factors Influencing Genetic Traits

• Sexual selection is driven by competition for mates and mate choice, leading to the evolution of traits that enhance reproductive success.
• Natural selection involves the differential survival and reproduction of individuals with advantageous traits, leading to their accumulation over time.
• Genetic variation is the diversity in DNA sequences among individuals.
• The environment, including climate, habitat, resources, and pollutants, can influence an organism's phenotype.

Genes, Chromosomes, and DNA

• Genes are physical and functional units of heredity that determine an organism's traits.
• Chromosomes are structures within the cell nucleus made of proteins and DNA, organized into genes.
• DNA is the molecule carrying genetic information for the development and functioning of an organism.

Roles of Genes and Traits

• Genes are fundamental to heredity and are central to the structure, function, and evolution of organisms, carrying instructions for cell growth and function.
• Traits are the observable characteristics of an organism.
• Species traits differentiate one species from another, including characteristics like body mass, length, or height.
• Individual traits make an organism different from others, which can be qualitative (eye color) or quantitative (height or blood pressure).

Historical Context and Mendel's Work

• In the 19th century, heredity was poorly understood, with traits believed to be a blend of parental characteristics, and the concept of genes was unknown.
• Gregor Johann Mendel discovered basic laws of inheritance through pea plants, revealing how traits are passed from parent to offspring through dominant and recessive traits.

Punnett Square

• A Punnett square is a table used to predict all possible outcomes for a genetic cross between two individuals with given genotypes.

Monohybrid and Dihybrid Crosses

• A monohybrid cross involves one gene.
• A dihybrid cross describes a mating experiment between two organisms that are identically hybrid for two traits.

Alleles

• Alleles are one of two versions of a DNA sequence at a given location.
• A dominant allele is expressed even when paired with a recessive allele.
• A recessive allele is only visible if paired with another recessive allele.

Genotype and Phenotype

• Genotype is the genetic makeup of an organism.
• Phenotype refers to the observable traits of an organism.
• Homozygous means carrying two identical alleles.
• Heterozygous means carrying different alleles.

Biodiversity

• Biodiversity comes from the Greek word "Bios" meaning life and the Latin word "Diversitas" meaning variety and refers to the abundance of life forms within a species.
• Low biodiversity indicates a small number of different life forms.

Factors affecting Biodiversity

• Pollution disrupts ecosystems and reduces clean water, food, and suitable habitats.
• Habitat destruction causes species to lose homes and resources, leading to extinction.
• High biodiversity indicates many types of species.
• Human influence can maintain landscapes and habitats.
• Climate regions with stable conditions.
• Geographical features can create microclimates and habitats.
• Habitat diversity provides unique resources.

Taxonomy

• Taxonomy is a branch of science for classifying and naming organisms.
• Taxonomy helps explain the diversity of life on Earth and how organisms are related.
• Classification involves arranging organisms into orderly groups based on similarities.
• Aristotle was the first person to classify living organisms, using a system based on Plants & Animals.

Linnaean System

• Carolus Linnaeus created the system we still use today.
• In the Linnaean system, each plant and animal is given a genus name followed by a species name in Latin.
• Binomial nomenclature is a biological system for naming organisms in two terms: genus and species.

Naming Rules

• Standardized naming rules use Latin or Greek.

• The genus is capitalized, and the species is not.

• Underlining is used for writing, and italics for print.

Taxonomic Ranks

• Domain is the highest taxonomic rank, classifying organisms based on fundamental differences in their genetic makeup.

Three Domains of Life

• Bacteria are unicellular organisms, some living in extreme environments and others not.
• Archaea can live in extreme environments and are evolutionarily distinct from bacteria.
• Eukarya are eukaryotes with nuclei and organelles, including animal, plant, and fungal cells.
• Kingdom is a high-level classification divided into subgroups at various levels.

Kingdoms

• Protista are single-celled, like algae.
• Archaea are the oldest organisms.
• Fungi use spores, some parasitic and infect hosts.
• Animalia includes all animals.
• Plantae ranges from mosses to giant trees.

Phylum, Class, Order, Family, Genus, and Species

• Phylum classifies organisms by structural and functional traits.
• Class refines classification based on additional shared characteristics.
• Order further narrows classifications.
• Family highlights organisms with significant shared traits.
• Genus groups similar species.
• Species is the lowest level.

Mnemonic

• The order from Domain to Species is: Differences, Kindgoms, PHylum, Class, Order, Family, Genus, and Species.

Trophic Levels

• Trophic levels represent the role an organism occupies in an ecosystem based on feeding relationships and energy flow.
• Producers are organisms that make their own food.
• Consumers must eat to get energy.

Types of Consumers

• Herbivores are primary consumers that eat plants.
• Carnivores eat meat and are predators.
• Omnivores eat both plants and meat.

Food Chains

• A food chain illustrates a linear sequence of energy and nutrient flow through an ecosystem.
• Decomposers break down dead organic matter, recycling nutrients back into the environment.
• Predators hunt living things for food.
• Prey are the hunted.
• Scavengers feed on the remains of dead animals.

Food Webs

• Food webs are interconnected food chains within the same ecosystem.
• The energy pyramid shows the amount of energy available at each trophic level, with less energy available at higher levels.

Symbiotic Relationships

Symbiosis

• Symbiosis is where two or more species live closely together.

Relationships in the Ecosystem

• Predation predator hunts and consumes prey
• Competition two or more organisms of same/different species compete for basic needs

Types of Competition

• Apparent : indirect, competing organisms have same predator
• Interspecific: competition two different species.
• Intraspecific: competition two same species.

Relationships in ecosystem

• Mutualism (+/+) is a cooperative partnership between two species where both benefit.
• Commensalism (+/-) is where one species benefits and the other is unaffected.
• Parasitism (+/x) is where a parasite feeds on a host without immediately killing it.

Environmental Laws

• R.A No. 9147, the Wildlife Resources Conservation & Protection Act, conserves and protects wildlife species and habitats and promotes ecological balance and biological diversity.
• R.A No. 9003, the Ecological Solid Waste Management Act. 2000, addresses solid waste problems and promotes segregation, recycling, and waste reduction practices.
• R.A Philippine Clean Air Act. 1999, protects & enhance air quality prompting sustainable development.

Biogeochemical Cycle

• Biogeochemical cycles are the movement of elements and compounds among the lithosphere, organisms, atmosphere, and hydrosphere; human activities can affect these cycles.
• Biosphere is Global ecosystem made up of Biota: Living organisms & Abiota: non living things

Spheres

• Lithosphere is the solid outer part of Earth, including the brittle portion of the mantle and the crust.
• Hydrosphere is the total amount of water on a planet, including water on the surface, underground, and in the air.
• Atmosphere is a mixture of gases surrounding the Earth that provide air to breathe and shields from UV radiation from the sun.

Cycles in Nature

• Water and minerals are recycled and reused by moving from the nonliving portion of the environment into living things and back.

Cycles

• Water cycle
• Carbon cycle
• Oxygen cycle
• Nitrogen cycle
• Phosphorus cycle

Water Cycle

• The water cycle is the continuous movement of water on the earth and in the atmosphere.
• Evaporation is the change from liquid water to gaseous water vapor.
• Condensation is the change from water vapor to liquid water.
• Precipitation forms in clouds as water vapor condenses into bigger droplets of water.
• Collection is when rain falls from clouds.

Carbon Cycle

• The carbon cycle illustrates how carbon flows between reservoirs in exchange.
• Carbon enters the atmosphere as CO2 is absorbed by autotrophs and consumes by animals.
• When animals and plants die and decompose, carbon is reabsorbed.

Oxygen Cycle

• The oxygen cycle involves the movement of free oxygen.
• Plants release oxygen during photosynthesis.
• Aerobic organisms respire oxygen.
• Animals exhale carbon used by plants for photosynthesis.

Nitrogen Cycle

• The nitrogen cycle converts nitrogen into many forms, passing through atmosphere, soil, organisms, and back to the atmosphere.
• Fixation converts nitrogen into forms that plants can absorb.
• Mineralization is when microbes decompose organic N from manure, organic matter, and crop residues to ammonium.
• Nitrification is carried out by specialized bacteria.
• Immobilization is when nitrate and ammonium are taken up by soil organisms, becoming unavailable to crops.
• Denitrification is when soil-dwelling denitrifying bacteria convert nitrates into nitrogen gas.

Phosphorus Cycle

• The phosphorus cycle involves the transformation and translocation of phosphorus in soil, water, and living or dead organic material.
• In the open cycle, phosphorus is carried through weathering or erosion to oceans from lands.
• Phosphate salts dissolved in water are absorbed by plants.
• Animals absorb phosphorus from plants or by consuming herbivores.
• Decomposers decompose, returning phosphorus needed by organisms.