Biology Maniak 2 Klausur 26 Juni

Nucleotides

The building blocks of DNA. Each consists of a sugar (deoxyribose), a phosphate group, and a nitrogenous base.

The Four Bases

Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).

Complementary Binding

$A$ always pairs with $T$ (via 2 hydrogen bonds); $G$ always pairs with $C$ (via 3 hydrogen bonds).

Determining the Complementary Strand

If given a strand, swap $A \leftrightarrow T$ and $G \leftrightarrow C$.

Example of Complementary Strand

Given 5'- A T C G G T A -3', the complementary strand is 3'- T A G C C A T -5'.

Cell Theory

All living organisms are composed of one or more cells; the cell is the basic unit of life; and all new cells arise from pre-existing cells.

Three Primary Functions of Cell Division

Growth, Repair/Replacement, Reproduction.

Gametes

Sex cells (sperm in males, eggs in females) that contain half the genetic material of a normal body cell.

Asexual Reproduction Product

Yields offspring that are genetically identical clones of the single parent (no genetic variation).

Gene

A specific segment of DNA along a chromosome that encodes the instructions for building a specific protein.

Human Chromosome Count

Humans have 46 chromosomes in total (23 pairs).

Sister Chromatid Structure

When DNA replicates, the chromosome consists of two identical joined copies called sister chromatids.

Somatic vs. Gamete Division

Somatic cells (body cells) are replaced via Mitosis; Gametes (sex cells) are produced via Meiosis.

Ploidy Definitions

Diploid ($2n$): Cells containing two complete sets of chromosomes; Haploid ($n$): Cells containing only a single set of chromosomes.

Zygote

A fertilized egg formed when a haploid sperm fuses with a haploid egg; it is diploid ($2n$).

Interphase

The preparation phase of the cell cycle, consisting of G1, S, and G2 phases.

Mitosis

The division of the nucleus, consisting of Prophase, Metaphase, Anaphase, and Telophase.

Cytokinesis

The division of the cytoplasm occurring at the end of telophase.

Sex Chromosomes

The 23rd pair of chromosomes that determine genetic sex.

Karyotype

A visual chart/image of an individual's collected chromosomes, used to scan for chromosomal abnormalities.

Meiosis

Occurs exclusively in germ cells to produce gametes, involving one round of DNA replication followed by two rounds of division.

At the end of Meiosis I

2 haploid cells are produced (homologous chromosomes separated).

At the end of Meiosis II

4 unique haploid cells are produced (sister chromatids separated).

Pedigrees

Family trees tracking genetic traits across generations.

Carrier

A heterozygous individual ($Bb$) who carries one copy of a recessive disease-causing allele but does not show symptoms.

Autosomal Recessive Rules

If two unaffected parents have a child who is shaded (affected), the condition must be recessive, and both parents must be carriers.

Incomplete Dominance

Neither allele is completely dominant over the other, resulting in an intermediate, blended phenotype.

Pleiotropy

One single gene influences multiple, seemingly unrelated physical traits.

Polygenic Inheritance

Multiple independent genes interact to determine one single physical trait, creating a continuous spectrum of variation.

Natural Selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

Adaptation

An inherited characteristic/trait that enhances an organism's ability to survive and reproduce in a specific environment.

Fossils

Preserved remnants or impressions of organisms from the past.

Age of Fossils

Fossils found in lower layers (strata) of sedimentary rock are older than those found in upper layers.

Radiometric Dating

A method used to determine the absolute age of a fossil or rock by measuring the decay of radioactive isotopes.

Transitional Forms

Fossils that bridge the evolutionary gap between ancient ancestors and modern species.

Basilosaurus

This ancient fossil whale possessed reduced, non-functional hind limbs, strongly suggesting that modern whales evolved from land-dwelling, four-legged mammalian ancestors.

Biogeography

The geographic distribution of species.

Comparative Anatomy

The study of similarities in the structure of different species.

Vertebrate Forelimbs

Human arms, whale flippers, and bat wings share the exact same bone structures.

Homology

The similarity due to shared ancestry.

Embryos

Vertebrate embryos (including humans and chicks) all look remarkably similar early in development and possess throat pouches and tails.

Bioinformatics

The use of computational tools to compare DNA and protein sequences.

Population

A group of individuals of the same species living in the same area at the same time that can interbreed.

Mutation

A random change in DNA sequence.

Microevolution

A generation-to-generation change in a population's allele frequencies within its gene pool.

Natural Selection (Microevolution)

Non-random shifts where the environment favors advantageous alleles.

Genetic Drift

A change in the gene pool of a population due to pure chance.

Bottleneck Effect

A drastic, random reduction in population size due to a disaster.

Founder Effect

A few individuals isolate themselves from a main population to colonize a new habitat.

Gene Flow

The gain or loss of alleles when fertile individuals migrate into or out of a population.

Sexual Selection

A form of natural selection where individuals with certain inherited characteristics are more likely to obtain mates.

Macroevolution

Evolutionary change above the species level, tracking major alterations over vast stretches of geologic time.

Speciation

The evolutionary process by which one species splits into two or more distinct species.

Non-branching Evolution (Anagenesis)

An ancestral species changes gradually over time into a single new species.

Branching Evolution (Cladogenesis)

An ancestral species splits into two or more distinct descendant species.

Mass Extinction

An event where a massive percentage of all living species on Earth are wiped out in a short geological timeframe.

Life first appeared on Earth

Approximately 3.5 billion years ago (as prokaryotes/bacteria).

Dinosaurs went extinct

Approximately 66 million years ago (at the end of the Cretaceous period).

Modern humans appeared

Approximately 300,000 years ago.

Continental Drift

The slow, continuous movement of Earth's tectonic plates over the mantle.

Biological Species Concept

A species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring.

Reproductive Barriers

Mechanisms that prevent species from interbreeding.

Allopatric Speciation

The formation of a new species due to a population being geographically isolated by a physical barrier.

Taxonomy

The scientific field focused on naming, defining, and classifying groups of biological organisms based on shared characteristics.

Clade

A group of species that includes an ancestral species and all of its descendants.

Phylogenetic Tree

A diagram that represents evolutionary relationships among species.