BIO 111b: General Biology I Lecture Review

Comprehensive practice flashcards in Question-and-Answer format covering introductory biology, cytology, cell division, gametogenesis, embryonic development, genetics, and ecology based on BIO 111b lecture notes.

Who is referred to as the "Father of Biology" and why?

Aristotle was the first to investigate living organisms scientifically, earning him the title "Father of Biology."

What are the five general and unifying concepts that govern all study and research in biology?

1. The cell is the basic unit of life. 2. Genes (consisting of DNA or RNA) are the basic unit of heredity. 3. Evolution accounts for the unity and diversity seen among living organisms. 4. All organisms survive by consuming and transforming energy. 5. All organisms maintain a stable internal environment.

What are stromatolites, and what evidence do they provide regarding the history of life on Earth?

Stromatolites are sedimentary accretions formed by the actions of cyanobacteria that provide fossil evidence of life on Earth dating back about $3.5\text{ billion years ago}$.

How does inductive reasoning differ from deductive reasoning in scientific inquiry?

Inductive reasoning draws a general conclusion from a number of specific observations, whereas deductive reasoning predicts specific results from a general premise.

What are the standard steps of the scientific method?

Make an observation, ask a question, form a hypothesis that answers the question, make a prediction based on the hypothesis, do an experiment to test the prediction, analyze the results, and report results (or modify the hypothesis and try again if the hypothesis is incorrect).

What are the four major categories of biological macromolecules?

1. Nucleic acids, 2. Proteins, 3. Carbohydrates, and 4. Lipids.

What striking organelle differences exist between animal cells and plant cells?

Animal cells have centrioles, centrosomes, and lysosomes, whereas plant cells do not. Conversely, plant cells contain chloroplasts, central vacuoles, other plastids, and a cellulose cell wall, which animal cells lack.

What contributions did Robert Hooke and Antony van Leeuwenhoek make to the discovery of cells?

Robert Hooke coined the term "cell" in his 1665 publication Micrographia after viewing cork tissue. Antony van Leeuwenhoek constructed microscopes magnifying up to $270\times$ and first observed bacteria, yeast, blood cells, and protozoa (which he termed "animalcules"), becoming known as the "Father of Microscopy."

What are the three core principles of the unified cell theory, and what was Rudolf Virchow's famous contribution?

1. All living things are composed of one or more cells. 2. The cell is the basic unit of life. 3. New cells arise from existing cells. Rudolf Virchow famously contributed "Omnis cellula e cellula" ("All cells only arise from pre-existing cells"), disproving spontaneous generation.

What are the primary differences between prokaryotic and eukaryotic cells?

Prokaryotes lack a membrane-bound nucleus (genetic material DNA or RNA is in a nucleoid), lack membrane-bound organelles, have cell sizes ranging from $0.1$ to $0.5\,\mu\text{m}$, and reproduce primarily by binary fission. Eukaryotes have a true nucleus enclosing chromatin (DNA with histones), possess membrane-bound organelles, range from $10$ to $100\,\mu\text{m}$, and divide by mitosis or meiosis.

What is the structural composition and thickness of the cell membrane according to the fluid-mosaic model?

The cell membrane is an extremely thin phospholipid bilayer measuring $75$ to $105\,\text{\AA}$ ($7.5\,\text{nm}$ total thickness, consisting of two outer protein/hydrophilic layers of about $2.0\,\text{nm}$ and a central hydrophobic lipid zone of about $3.5\,\text{nm}$) with embedded transmembrane and peripheral proteins, cholesterol, and glycolipids.

How do rough endoplasmic reticulum and smooth endoplasmic reticulum differ in structure and function?

Rough endoplasmic reticulum consists of flattened cisternae encrusted with ribosomes and functions in the isolation, synthesis, and transport of proteins. Smooth endoplasmic reticulum consists of tubular cavities lacking ribosomes and functions in the synthesis and transport of lipids and steroids.

What are the structural features of a mitochondrion?

A sausage-shaped, threadlike, or round organelle bounded by a double membrane envelope; the inner membrane folds into inward partitions called cristae enclosing a matrix containing circular DNA, ribosomes, phosphate granules, and enzymes for the citric acid cycle (TCA) and oxidative phosphorylation.

What are lysosomes, and why are they referred to as the "suicide bags" of the cell?

Lysosomes are spherical sacs ($0.25$ to $0.8\,\mu\text{m}$ in diameter) bounded by a single membrane containing hydrolytic digestive enzymes (e.g., acid-phosphatase, RNAase, DNAase). They digest food, destroy worn-out organelles, and can destroy the entire cell after its functions are complete or when it dies.

What are the four main types of passive transport across cell membranes?

1. Simple diffusion (movement down a concentration gradient without energy). 2. Facilitated diffusion (carrier-mediated transport of large molecules via membrane transport proteins without energy). 3. Osmosis (movement of water across a semi-permeable membrane). 4. Filtration (movement of solutes and water driven by cardiovascular pressure).

What is the hierarchical sequence of taxonomic categories from broadest to most specific?

Kingdom, Phylum, Class, Order, Family, Genus, Species (with Domain and Life often recognized above Kingdom, and Subfamily occasionally placed between Family and Genus).

What is the difference between a monotypic genus and a polytypic genus?

A monotypic genus contains only a single species, whereas a polytypic genus contains more than one species (for example, lions and tigers are grouped under the polytypic genus Panthera).

What are the phases of the cell cycle and the specific events that occur in each?

The cell cycle consists of Interphase and the Mitotic (M) phase. Interphase includes: $G_1$ (cell growth and preparation for replication), $S$ (DNA synthesis/replication and centrosome duplication), and $G_2$ (cell growth and preparation for mitosis). The M phase comprises mitosis (karyokinesis) and cytokinesis, producing two daughter cells.

What are the five sequential stages of Prophase I in meiosis?

1. Leptotene (chromosomes condense and appear single). 2. Zygotene (homologous chromosomes pair in synapsis to form bivalents). 3. Pachytene (bivalents shorten, thicken, and become clearly visible). 4. Diplotene (homologues pull slightly apart, revealing chiasmata between non-sister chromatids). 5. Diakinesis (centromeres move apart, nucleoli and nuclear membranes disappear, and spindle fibers form).

Why is Meiosis I called a reduction division while Meiosis II is called an equatorial division?

Meiosis I is a reduction division because homologous chromosomes separate, reducing the ploidy level from diploid ($2n$) to haploid ($1n$). Meiosis II is an equatorial division because sister chromatids separate while the number of chromosomes remains the same ($1n$ to $1n$).

How do the cellular outcomes of spermatogenesis and oogenesis differ in terms of functional gametes produced?

Spermatogenesis produces four equal-sized, functional haploid spermatozoa from each primary spermatocyte. Oogenesis produces only one functional haploid ovum (conserving cytoplasm and nutrients) and two or three non-functional polar bodies that eventually degenerate.

What are the structural components of a mature human spermatozoon?

It consists of a head ($2.5\,\mu\text{m}$ long) containing the haploid nucleus and an acrosome with hydrolytic enzymes, a short neck containing two perpendicular centrioles, a middle piece packed with mitochondria, and a tail with an axial filament containing a $9+2$ array of microtubule fibres.

What hormonal feedback mechanism controls testosterone secretion and sperm production in males?

GnRH from the hypothalamus stimulates the anterior pituitary to secrete LH (stimulating Leydig cells to produce testosterone) and FSH (stimulating Sertoli cells). Elevated testosterone exerts negative feedback on GnRH and LH. If spermatogenesis is too rapid, Sertoli cells release inhibin, which inhibits FSH secretion by the anterior pituitary.

What hormonal events trigger ovulation and the subsequent formation of the corpus luteum during the menstrual cycle?

Estrogen produced by developing granulosa cells rises to a peak midpoint level, triggering a massive surge of Luteinizing Hormone (LH) and FSH from the anterior pituitary, which causes ovulation (around day $14$). LH then stimulates the remaining Graafian follicle to transform into the progesterone-secreting corpus luteum.

What are the acrosome reaction and the cortical reaction during fertilization?

The acrosome reaction occurs when the sperm head releases hydrolytic enzymes to degrade the glycoprotein coat (zona pellucida/vitelline membrane) allowing fusion of gamete membranes. The cortical reaction involves the release of cortical granules to thicken the membrane into an impenetrable fertilization membrane, preventing polyspermy.

What embryonic structures and adult tissues originate from the ectoderm, mesoderm, and endoderm germ layers?

Ectoderm gives rise to the nervous system, neural tube, receptors, epidermis, hair, and glands. Mesoderm divides into epimere (somites: dermis, voluntary muscles, vertebrae), mesomere (kidneys, gonads), and hypomere (peritoneum, heart, gut muscle, blood). Endoderm forms the primitive gut lining, respiratory lining, liver, pancreas, thyroid, and bladder epithelium.

How do oviparity, ovoviviparity, and viviparity differ as modes of internal fertilization?

In oviparity, fertilized eggs are laid outside the body and nourished by yolk. In ovoviviparity, fertilized eggs are retained inside the female receiving nourishment from the yolk until hatching right before or during laying. In viviparity, young develop directly inside the mother's body, receiving maternal nutrition, and are born live.

What are the primary forms of asexual reproduction found in animals?

Binary fission (parent divides into two identical cells, e.g., Amoeba), budding (outgrowth develops on parent and detaches, e.g., Hydra), fragmentation (body breaks into pieces that each grow into an individual, e.g., Planaria), regeneration (detachment of a limb grows a new individual, e.g., Echinoderms), and parthenogenesis (egg develops without fertilization, e.g., bees, aphids, Komodo dragons).

What is the function of human chorionic gonadotropin (hCG) during early pregnancy?

Secreted by the chorion of the blastocyst, hCG prevents the breakdown of the corpus luteum, maintaining progesterone secretion to preserve the uterine endometrium for the developing embryo.

What occurs during the three stages of human labor?

Stage one: The cervix thins (effaces) and dilates to a full width of $10\,\text{cm}$, and the amniotic sac bursts. Stage two: The baby is pushed and expelled from the uterus through the birth canal. Stage three: The placenta and fetal membranes are detached and expelled from the uterus within a few minutes.

State Mendel's First Law and Second Law of inheritance.

Mendel's First Law (Law of Segregation) states that an organism's characteristics are determined by paired alleles that separate during gamete formation so each gamete carries only one allele. Mendel's Second Law (Law of Independent Assortment) states that the segregation of one gene pair occurs independently of the segregation of another gene pair.

What phenotypic ratio results from an $F_1$ dihybrid cross ($RrYy \times RrYy$) with independently assorting traits?

A $9:3:3:1$ phenotypic ratio ($9$ Round Yellow, $3$ Round Green, $3$ Wrinkled Yellow, and $1$ Wrinkled Green).

Why can a father not transmit an X-linked recessive trait directly to his son?

A father contributes his $Y$ chromosome to his son, while his $X$ chromosome is transmitted exclusively to his daughters. Therefore, sex-linked traits on the $X$ chromosome are passed from fathers to grandchildren via carrier daughters.

How do Lamarckism and Darwinism differ regarding the mechanism of evolutionary change?

Lamarckism states that organs develop through use or disappear through disuse and that all acquired traits are transmitted to offspring, discrediting the struggle for existence. Darwinism is based on the struggle for existence and natural selection (survival of the fittest), where only heritable, advantageous variations are preferentially preserved and passed to succeeding generations.

How does an S-shaped (sigmoid) population growth curve differ from a J-shaped population growth curve?

An S-shaped curve exhibits a slow initial increase, followed by rapid exponential growth, and then levels off as environmental resistance takes effect. A J-shaped curve shows density increasing rapidly and exponentially until it stops abruptly due to environmental changes or resource exhaustion.

How does the pitcher plant differ from typical plants in terms of its trophic classification?

Virtually all plants are autotrophic producers, but the pitcher plant is an exception that acts as a consumer by trapping insects in a sticky substance within its flower to absorb nutrients.

What is a keystone species, and what happens if one is removed from a community?

A keystone species plays an exceptionally important role in maintaining community structure. If removed, prey species that lack other natural predators (e.g., mussels and sea urchins controlled by predatory sea stars) experience explosive population growth, outcompeting and driving out other species and destroying the community.

How does the relationship between a clownfish and a sea anemone demonstrate mutualism?

The clownfish gains protection from predators via the anemone's stinging tentacles and feeds on prey remains, while the anemone gains food attracted by the clownfish's bright colors and absorbs nutrients from clownfish feces.

Why is the number of trophic levels in an ecological food chain generally limited to four or five?

At each successive trophic level, approximately $90\%$ of energy is lost as heat, metabolic work, or animal waste, leaving only about $10\%$ available to the next level. Eventually, there is insufficient energy remaining to sustain organisms at a higher trophic level.

What is the primary difference between intraspecific competition and interspecific competition?

Intraspecific competition occurs between individuals of the same species competing for identical limited resources (often driving specialization and natural selection), while interspecific competition occurs between members of different species sharing a contested limiting resource.