Biology Chapter on Evolution and Homeostasis

Evolution

• Evolution is the central theory of biology
• It answers questions like:
  • Why do bacteria develop resistance to antibiotics?
  • Why do fatal genetic disorders still exist?
  • Why are some people more likely to get cancer?
• Understanding evolution helps make scientific discoveries.
• Example: Sickle cell anemia, a genetic blood disorder, affects 1/365 births in people of African descent.
• Scientists wondered how such a harmful trait is so common, finding that heterozygous individuals (having one copy of the normal gene and one copy of the abnormal gene) have an advantage against the disease.

Evolution: Change

• Biological evolution is the change in characteristics of a population over generations.
• Evolutionary changes are inherited via genes.
• All species on Earth today are descendants of a single common ancestor.

How Evolution Occurs

• Mutations (e.g., UV light, viruses) create genetic differences in a population.
• Random mutations can create genetic differences in organisms, impacting traits' positive or negative effects on reproduction and inheritance.

Public Perception of Evolution

• Life on Earth arose once, and all living things are descendants of that single original cell.
• The differences between organisms are results of evolution.
• Galileo's trial in 1633, where he was ordered to stand trial for heresy, threatened with torture for his belief in heliocentrism (the sun is at the center of the galaxy, and Earth and other planets orbit it) conflicts with some statements in the Bible. This shows how scientific understanding conflicts with some religious beliefs.
• 98% of scientists and 76% of the US public believe in human evolution.

Darwin and the Voyage of the Beagle

• Darwin was a medical school graduate initially uncertain about his career path.
• He accepted a position as a naturalist on a voyage around the world in 1831, including the Galapagos Islands.
• Darwin observed that birds' bodies looked similar but with different diets and beaks.
• Darwin's observations about evolution include:
  • Offspring inherit traits from their parents.
  • Species produce more offspring than the environment can support.
  • Variations/traits give some species a better chance to survive and reproduce than other species in their environment.

Evidence for Evolution

• Fossil Evidence: Evidence for common descent is found in fossils, which offer a sequence of evolutionary change within lineages (e.g., the horse).
• Shared Developmental Pathways: Similarities in vertebrate embryos suggest a common ancestor.
• Anatomical Similarities: Mammalian forelimbs have similar underlying structures despite different functions.
• Vestigial Structures: Structures or behaviors that are remnants of past evolutionary adaptations, like human tailbones or muscles attached to our ears.
• DNA Similarities: Species within the same genus have similar DNA, while distantly related species have less similar DNA.

Misconceptions About Evolution

• "Evolution is just a theory" - Scientific theories are ideas repeatedly tested using varied methods, not just guesswork.
• "Evolution explains the origin of life" - Evolution explains how populations change over time, not the origin of life itself.
• "Individuals evolve" - Evolution happens at the population level, not an individual.
• "Organisms evolve on purpose" - Evolution occurs due to random and non-random events.

Speciation

• Species are groups of populations in nature that can interbreed and produce fertile offspring, not applicable to asexually reproducing organisms.
• Speciation is the formation of two species from one original species.

How New Species Arrive

• Allopatric speciation: a species splits due to physical separation, then difference in traits arise. -Sympatric speciation: a species splits while living in the same habitat. Adaptive Radiation: one species spreads to various habitats, developing into multiple species.

Gametic Barriers

• Eggs and sperm of different species cannot fuse.
• Hybrid inviability: offspring do not survive.
• Hybrid infertility: offspring can't reproduce.

Other Questions

• Review topics covered in the lessons.

Population Genetics and Hardy-Weinberg

• Evolution happens at the population level.
• A population is a group of the same species living in the same area Interbreeding and creating offspring.
• Alleles are different versions of a Gene existing in a population, allele frequency is the measure of how often an allele shows up in a population
• Gene pools represent the number of different alleles available to a population, including recessive alleles.

Allele Frequencies

• Allele frequencies are the likelihood of having sperm or eggs with a specific allele.
• These have applications in figuring out the frequency of different genotype outcomes in future generations.

Population Genetics Mechanisms

• Natural selection
• Genetic drift
• Founder effect
• Bottleneck effect
• Gene flow
• Non-random mating

Brief History of Life on Earth

• The fossil record indicates that evolutionary change is not constant.
• Punctuated equilibria refers to periods of little change followed by rapid change.
• Cambrian explosion: increased oxygen in the environment, enabling the evolution of complex life forms 540 million years ago.

From Tikaalik to TikTok

• Amphibians: the first land-dwelling tetrapods, emerged around 500 million years ago.
• Reptiles (including birds): lay amniotic eggs, eliminating the need for reproduction in water, and allowing better parent-to-child protection.
• Primates: highly mobile thumbs, larger brains, tree-dwelling lifestyle, which makes modern primates an exception to the "all ancestors were primates" assumption.

Social Darwinism and Eugenics

• The popularity of Social Darwinism led to a revival of eugenics.
• Eugenics is the belief that humankind can be improved through selective breeding and the removal of "undesirable traits."
• The term "race" often means a mix of social class, culture and genetics.
• The belief that humans can improve through selective breeding or the removal of groups is inaccurate and racist.

The Evolution of Modern Humans

• Humans are not descended from chimpanzees, but shared a common ancestor.
• Many intermediate fossil species have been found.
• Modern humans and Neanderthals interbred.
• Being a night owl and napping during the day were traits influenced by Neanderthal variants.

Neanderthals

• First Homo neanderthalensis fossils were discovered in 1856 in Germany, dated at 40,000 years ago.
• Neanderthals had brains larger than modern humans and buried their dead.

Anatomy and Physiology

• Anatomy: the study of the structure of body parts.
• Physiology: the study of how the body functions.
• Basic ideas:
  • Exchange with the environment
  • Animal tissue types
  • Communication and homeostasis
  • Thermoregulation and energy expenditure

Tissue Types

• Epithelial Tissue: Covers body surfaces and lines internal organs.
• Connective Tissue: Supports and connects body parts (e.g., bone, blood).
• Muscle Tissue: Enables movement (e.g., skeletal, smooth, cardiac).
• Nervous Tissue: Conducts nerve impulses.

Communication and Homeostasis

• Nervous system - Electrical and chemical signals
• Endocrine system- Hormones
• Homeostasis regulation of internal conditions.

Thermoregulation

• Maintaining internal body temperature
• Behavioral and Physiological Mechanisms: insulation, blood flow regulation, countercurrent exchange.

Gain and Loss of Heat

• Radiation: heat emission.
• Evaporation: water removal (e.g., sweating).
• Convection: heat transfer by air movement.
• Conduction: heat transfer by contact.
• Metabolic Rate: the sum of all energy used by an organism, affects heat production.

Test your knowledge on evolution concepts, including misconceptions, vestigial structures, and evidence supporting evolution. Additionally, assess your understanding of the endocrine system, feedback loops, and their roles in maintaining homeostasis.