Biological Anthropology and Evolution

• Biological Anthropology is the scientific study of humans and non-human primates, studying them as biological organisms within an evolutionary framework.
• Biological Anthropology seeks to understand human origins, how humans have changed over time, similarities and differences among humans worldwide, and ongoing human evolution.
• Haldane's rule states the heterogametic sex is sterile in hybrids.
• Evolution is defined as the change in trait frequency within a population over time.
• Variation refers to differences among individuals in a population.
• Natural selection is the process where heritable features enhancing an organism's fitness increase in frequency over generations.
• Reproductive advantage (fitness) relates to the capability to survive, reproduce, and achieve reproductive success.
• Organisms with a reproductive advantage reproduce more than others of their species.
• Darwinism involves natural selection acting on inherited genetic variation.
• Lamarckianism suggests organisms pass on traits acquired during their lifetime.
• Uniformitarianism is the concept that geological processes occurring today also happened in the past, slowly changing the Earth.
• Artificial selection is selection done by humans, like dog breeds and crops.

Taxonomy

• Genus is a group of closely related species.
• Species is the most basic unit of classification.
• Phylogeny is a tree showing how organisms are related through common descent.
• Codon is 3 mRNA bases that specifies an amino acid in the polypeptide chain

Common Ancestry and Descent

• Organisms sharing a common feature inherited from a common ancestor are related through common descent.
• Homology is a common feature shared by two or more organisms inherited from a common ancestor.
• A heritable trait is encoded in DNA and passed to offspring.
• Adaptation is a trait favored by natural selection that aids an organism in surviving and reproducing in its environment and is the outcome of natural selection.
• Adaptive radiation occurs when species evolve from a common ancestor, dispersing to new environments and developing unique adaptations.

Genetic Drift

• Genetic drift is a random change in allele frequency within a population.
• Genetic drift is strongest in small populations.
• Genetic drift can lead to fixation, where one allele becomes the only allele in a population, or loss of traits.
• Bottleneck is a significant reduction in population size due to a catastrophic event, leading to a drastic reduction in genetic diversity.
• The Founder Effect occurs when a small group of individuals starts a new population.
• A new population formed by a small group may have less genetic diversity and certain traits may become more common or rare by chance.
• Gene flow is the movement of genes from one population to another.
• Gene flow increases genetic diversity.
• Gene flow is connected to migration, resulting in admixture

Admixture, Base Pairs, and Mutation

• Admixture is the exchange of genetic material between previously isolated populations due to gene flow.
• Admixture is a source of new variation and can lead to new traits under selection.
• A base pair consists of two nucleotides connected by hydrogen bonds.
• Mutation refers to errors during cell division and DNA replication, creating genetic variation.

Mendel's Laws of Inheritance

• For each gene, organisms inherit one allele (gene version) from each parent.
• Typically, only one allele is expressed.
• It is equally likely for an organism to inherit either of its parent's alleles.
• Genes are inherited independently of one another

Genes

• A gene is a sequence of DNA that codes for the creation of a protein.
• A gene is the fundamental unit of heredity.
• An allele is a different version of the same gene.
• An individual inherits one allele from each parent
• Alleles can be dominant (the trait appears no matter the other allele) or recessive (the trait only appears if the dominant allele isn't present).
• Recessive trait only appears if the dominant allele is not present.
• Dominant trait appears no matter what the other allele is.
• Codominance occurs when both alleles of a gene are expressed, and the phenotype is blended.
• AB blood type is an example of codominance.
• Genotype is the genetic makeup of an organism.
• Genotype refers to which alleles a person has.
• Homozygous means having two identical alleles for a particular gene.
• Can be homozygous dominant (AA) or homozygous recessive (aa).
• Heterozygous means having two different versions of a gene, one inherited from each parent.
• A heterozygous genotype can have a higher fitness than either homozygous genotype.
• Heterozygotes may have an advantage because they have beneficial traits from both alleles
• Phenotype relates to observable features of an individual

DNA, Nucleotides, Chromosomes & Genetic Processes

• DNA (deoxyribonucleic acid) has a double-helix structure and is composed of nucleotides; it codes for building the entire body.
• A nucleotide is a structural unit of nucleic acids that consists of a phosphate, 5-carbon sugar, and a nitrogenous base.
• A base pair is two nucleotides connected by hydrogen bonds.
• In DNA, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G).
• Genome refers to all of an organism's DNA (genes and non-coding DNA).
• A chromosome (autosomal and sex) is a structure composed of coiled up DNA
• Humans have 46 chromosomes, or 23 pairs.
• Sex chromosomes are X and Y.
• Transcription & Translation relates to mRNA (messenger RNA) and codon.
• Amino acids are the building blocks of proteins
• Protein is a molecule coded for by a gene and created during translation.
• Mitosis is cell division that occurs in somatic cells (all cells in your body except sex cells).
• Meiosis (and Recombination) is strictly for the production of gametes.
• Meiosis involves 2 divisions.
• Meiosis forms cells that are not identical due to recombination.
• Meiosis results in 4 genetically distinct haploid cells.

Somatic vs Germline cells

• Somatic cells are all body cells.
• Germline cells : Sperm and egg cells which are only germline mutations are inherited and relevant for evolution
• A zygote is a diploid cell resulting from the fusion of two haploid gametes.
• Diploid cell contains two complete sets of chromosomes.
• Haploid cell contains only one set of chromosomes.
• Diploid cells occur in most cells, while haploid cells are in sperm and egg cells.

Selection

• Directional selection is a form of natural selection where one extreme version of a trait is favored, shifting the population in one direction which causes gradual shifts in allele frequencies toward the favored trait
• The increase in beak size among finches during droughts exemplifies directional selection.
• Stabilizing selection is a natural selection process favoring average traits and selects against extreme traits.
• Balancing/diversifying selection is a type of natural selection where multiple alleles are maintained , thus preserving genetic diversity.

Heterozygote Advantage, Convergent Evolution and Traits

• Heterozygote advantage is when a heterozygous genotype has a higher fitness than either homozygous genotype.
• Convergent evolution (homoplasy) is when species evolve similar traits independently, not due to recent shared common ancestry.
• Traits from convergent evolution are termed homoplasies.
• A Mendelian trait is controlled by one gene, while a polygenic trait is controlled by many genes.
• Pleiotropy is a type of genetic expression where one gene affects multiple traits.
• Phenotypic plasticity (epigenetics) is an organism's ability to change its physical characteristics, behavior, and physiology, in response to environmental conditions.
• Population means a group of individuals of the same species living in the same area and interbreeding

Microevolution, Macroevolution and Species

• Microevolution includes small-scale changes in allele frequencies within a single population over a short period.
• Macroevolution are Large-scale evolutionary changes leading to the formation of a new species or higher taxonomic groups over long periods of time
• Biological Species Concept suggests a species is a group of interbreeding organisms that can produce fertile offspring and are reproductively isolated from other such groups.
• Ecological Species Concept suggests a lineage or a group of closely related lineages that live in a specific adaptive niche and are different enough from other groups in the same area
• Parapatric Speciation refers to a species as a group of organisms that are distinctly different from other groups and share a common ancestry focused on heritable genetic differences that set one population apart from others

Speciation

• Speciation encompasses allopatric, parapatric, and sympatric:
  • Allopatric Speciation occurs when a species is divided by a barrier limiting gene flow, and each population adapts to different environments.
  • Parapatric Speciation: population is partially separated and each evolves their own adaptations based on their range when their ranges overlap, they may still interbreed.
  • Sympatric Speciation: where there is no geographical barrier, speciation is occurring in the same area through factors other than geography.
• Reproductive isolation is when different species are unable to breed and produce healthy offspring.
• Hybridization consists of interbreeding between species, which may or may not produce fertile offspring.
• Niche is the specific context in which a population exists, including it's role and position a species has in its environment.

Recombination and Darwin's Contributions

• Recombination occurs when genes are rearranged on their respective chromosomes during meiosis
• Recombination is an important source of new genetic variation
• Darwin's theory proposed that species evolve over time which built on the previous contributions of Lamarck's Darwin's concept of survival of the fittest
• Darwin's important observation for natural selection consists of: More offspring are produced than the food supply can support (competition for resources), there is heritable and none heritable variation within all or most species this heritable variation is what leads to natural selection or survival of the fittest
• Acquired traits are not inherited-Evolution occurs through genetic variation and natural selection
• What is necessary for evolution to occur? Genetic Variation – Differences in DNA among individuals in a population, Heritability - Traits must be passed from one generation to the next, Time - Evolution happens across multiple generations and More offspring is produced than there is food, meaning not all can survive+Variation within a species
• Some traits arise due to convergent evolution, where unrelated species evolve similar traits due to similar environmental pressures
• There is no such thing as typological thinking. Evolutionary thinking recognizes species as populations that change over time due to genetic variation and natural selection
• Humans share a more recent common ancestor with chimpanzees and bonobos than with other primates like gorillas or orangutans

Taxonomy of Humans

• Kingdom: Animalia • Phylum: Chordata • Class: Mammalia • Order: Primates • Family: Hominidae • Genus: Homo • Species: Homo sapiens
• Recombination shuffles genetic material during meiosis, increasing genetic diversity and creating new trait combinations that natural selection can act upon while continuous variation occurs when a trait is controlled by multiple genes

Mendel's Laws and Exceptions

• Mendel's Laws of Inheritance has exceptions to these rules as does "linkage disequilibrium" change Mendel's fourth law for genes on the same chromosome:
  • 1. Law of segregation: Each individual has two alleles for a gene, and they separate during gamete production
  • 2. Law of Independent Assortment – Genes for different traits assort independently during meiosis
  • 3. Law of Dominance - Some alleles are dominant over others like codominance
• Linkage disequilibrium – Genes close together on the same chromosome are often inherited together, violating independent assortment
• Deviation from Hardy-Weinberg equilibrium is when evolution is suggested to be occurring through genetic drift or forces of evolution
• Random forces of evolution are Mutation and Genetic drift which can increase or decrease diversity
• Stronger effects occur in smaller populations, where genetic drift plays a larger role

Factors Influencing Selection

• Factors influence how effective or how rapidly selection can act, and evolution can occur through Genetic variation, lifespan, population size and how strong the selection pressure is
• Dominant traits are expressed immediately and subject to stronger selection. , while Recessive traits can persist in populations as hidden alleles in heterozygotes and Selection acts on the phenotype, but evolution occurs through changes in genotype
• Forces of evolution have shaped human populations by driving adaptations to different environments: varying skin colors, sickle cell, tibetan people with rosy
• Alleles for a detrimental phenotype like sickle cell, are maintained in certain human populations (e.g., sickle cell in Africa because There is a heterozygote advantage to having sickle cells in certain parts of the world like Africa
• Convergent evolution is when a species evolves similar traits independently (not because of a recent common ancestor.)
• Example is: light skin developed independently in Asia and Europe
• X-linked disorders more common in males because Males only have one x chromosome, so recessive x-linked mutations are always expressed,
• Humans can go from genes to traits through the process of1. transcription: DNA is copied into messenger rna (mRNA) 2. translation: Messenger RNA is turned into a protein or Gene → RNA → Protein → Trait

Genetic Code

• The genetic code is redundant because multiple codons can code for the same amino acid
• This redundancy in the code helps protect organisms from mutations
• Environmental factors can affect individuals.
• Why are species so hard to define? What are some concepts that scientists try to apply to categorize populations into species like Biological species concept or phylogenetic/ecological concept
• Allopatric speciation caused by geographic isolation is the most common form of speciation because Geographic separation prevents gene flow and leads to Gene flow • Alleles means alternative versions of a gene that are distinguished from one another by their differing effects on the phenotypic expression of the same gene
• Homologous chromosomes undergo crossing over during meiosis