Biology Overview and Scientific Process

The total number of protons and neutrons in an atom's nucleus.

Atoms of the same element with the same number of protons but different numbers of neutrons.

The force of attraction that holds atoms together in molecules.

A type of chemical bond formed when two atoms share one or more pairs of electrons.

A type of chemical bond formed when one atom donates an electron to another atom, creating oppositely charged ions that attract each other.

A weak bond between a hydrogen atom and an electronegative atom, often oxygen or nitrogen.

The tendency of water molecules to stick together due to hydrogen bonds.

The tendency of water molecules to stick to other surfaces.

An error during meiosis where homologous chromosomes or sister chromatids fail to separate properly, resulting in an abnormal number of chromosomes in daughter cells.

A photographic representation of an individual's chromosomes, arranged in pairs from largest to smallest, used to detect chromosomal abnormalities.

A genetic condition characterized by an extra copy of chromosome 21, resulting in distinctive physical features and developmental challenges.

The study of heredity and how traits are passed down from parents to offspring.

Alternative forms of a gene that occupy the same position (locus) on homologous chromosomes.

A cross between two individuals heterozygous for a single trait.

A cross between two individuals heterozygous for two different traits.

The principle that allele pairs separate independently during gamete formation, leading to independent assortment of traits in offspring.

The division of the cytoplasm to create two daughter cells after mitosis or meiosis.

A process where a cell divides into two identical daughter cells, each with the same number of chromosomes as the parent cell. It involves the duplication of chromosomes and their distribution into two nuclei.

A pair of chromosomes that have the same genes at the same loci, one from each parent.

Specialized cells involved in sexual reproduction that carry a single set of chromosomes (haploid).

A process where a cell divides twice, resulting in four daughter cells, each having half the number of chromosomes as the parent cell. It involves crossing over and independent assortment, leading to genetic diversity.

The exchange of genetic material between homologous chromosomes during prophase I of meiosis, leading to increased genetic variability in offspring.

Cells that make up the body tissues of an organism, containing a full set of chromosomes (diploid) in human (46).

The uncontrolled division of cells that can lead to the formation of tumours and the spread of cancer.

The development of barriers that prevent interbreeding between populations, leading to the formation of new species. These barriers can arise due to adaptations to different environments, such as food sources, mating preferences, or predators.

Speciation that occurs without geographical isolation. It can happen through mechanisms like polyploidy (chromosome duplication), habitat differentiation (using different resources within the same area), and sexual selection (mate preference driving species divergence).

A form of sexual selection where mate preferences lead to the evolution of distinct traits in different populations, eventually resulting in speciation. Think of how the peacock's extravagant tail feathers, a result of mate choice, helped them diverge from their ancestors.

The rapid evolution of multiple species from a common ancestor, often observed in isolated environments like islands. This occurs due to repeated isolation and recolonization, and the exploitation of different ecological niches.

Regions where closely related species interact and interbreed, producing hybrid offspring. The outcome of these interactions can lead to reinforcement (strengthening reproductive barriers), fusion (merging of species), or stability (continued production of hybrids).

Fossils provide evidence for the differences between past and present organisms and trace evolutionary sequences.

The fossil record documents the extinction of species and the transitions they underwent.

They bridge the gap between extinct and living species, like the discovery of Pakicetus and Rodhocetus, demonstrating how whales evolved from terrestrial mammals.

Similarities in traits due to shared ancestry. Structural and molecular homologies connect species.

Remnants of ancestral characteristics that are no longer essential for survival.

Depictions of evolutionary relationships and branching patterns based on anatomical and molecular similarities.

Natural selection acts on populations, not individuals, affecting heritable traits. Evolution is not goal-directed.

It refers to the changes in the gene pool of a population over time. Individuals don't evolve, but populations do.

Genes located on sex chromosomes, like the X chromosome, have unique inheritance patterns.

X-linked disorders are more likely to affect males because they only have one X chromosome. If they inherit a recessive disorder allele, there's no other copy to 'mask' it.

Nucleic acids, like DNA and RNA, are made of long chains of building blocks called nucleotides. Each nucleotide has three parts: a nitrogenous base, a sugar, and a phosphate group.

DNA is a double-stranded helix. Each strand contains a sequence of nucleotides, and the two strands are complementary, meaning they pair up like puzzle pieces. A pairs with T, and C pairs with G.

DNA replication is the process of making a copy of DNA. It starts with the two strands separating. Each strand acts as a template for a new strand, using free nucleotides. This results in two new DNA molecules, each with one old strand and one new strand.

Transcription is the process of making RNA from DNA. Translation is the process of making a protein from RNA. So essentially, DNA encodes information that's transferred to RNA, then to a protein. This protein carries out the instructions encoded in the DNA.

Evolution is the change in the characteristics of a population over time. It's driven by natural selection, where individuals with traits better suited to their environment are more likely to survive and reproduce, passing those advantageous traits on to their offspring.

Darwin's theory of evolution emphasizes common ancestry (everything is related), descent with modification (changes accumulate over time), and natural selection as the driving force behind these changes. The environment plays a key role in shaping the evolution of life.