Living Environment Weaknesses

Mitosis

Type of cell division for growth and repair that produces 2 identical diploid cells.

Meiosis

Type of cell division that produces 4 non-identical haploid gametes for reproduction.

Purpose of Mitosis

Growth and repair in body (somatic) cells.

Purpose of Meiosis

Production of sex cells (sperm and egg).

Crossing Over

Exchange of genetic material during meiosis that increases variation.

Independent Assortment

Random distribution of chromosomes in meiosis; adds variation.

DNA Structure

Double helix made of nucleotides with bases A–T and C–G.

DNA Function

Sequence of bases codes for amino acids to make proteins.

Mutation

Change in DNA base sequence that may alter protein shape or function.

Types of Mutations

Substitution, insertion, deletion.

Inherited Mutations

Only mutations in gametes (sex cells) can be passed to offspring.

Gene Expression

Process where some genes are turned on or off depending on environment.

Example of Gene Expression

Hydrangea flower color changes with soil pH.

Nucleus

Holds DNA and controls the cell.

Ribosomes

Make proteins.

Mitochondria

Produce energy (ATP) through respiration.

Cell Membrane

Controls what enters and leaves the cell.

Endoplasmic Reticulum (ER)

Makes and folds proteins and lipids.

Golgi Apparatus

Packages and ships proteins and lipids.

Lysosomes

Break down waste and old cell parts.

Cytoplasm

Jelly-like fluid where cell activities happen.

Cytoskeleton

Gives shape and helps the cell move.

Chloroplasts

Use sunlight to make food (photosynthesis).

Cell Wall

Rigid layer for structure and protection (plants only).

Vacuole

Stores water, food, and waste (large in plant cells).

Receptor Molecules

Proteins on cell membrane that receive chemical signals.

Hormones

Chemical messengers like insulin that bind to specific receptors.

Lock and Key Model

Each receptor fits only one hormone.

Energy Flow in Ecosystems

Energy from the Sun flows through producers → consumers → decomposers.

Producers (Autotrophs)

Make their own food through photosynthesis.

Consumers (Heterotrophs)

Eat producers or other consumers.

Decomposers

Break down dead organisms and recycle nutrients.

Energy Pyramid Rule

Only about 10% of energy moves up each trophic level.

Energy Pyramid Order

Producer → Primary Consumer → Secondary Consumer → Tertiary Consumer → Decomposer.

Biodiversity

Variety of life that increases ecosystem stability.

Human Impacts

Deforestation, pollution, and overharvesting reduce stability.

Sustainable Practices

Reforestation, crop rotation, and habitat restoration.

Photosynthesis Equation

CO₂ + H₂O → C₆H₁₂O₆ + O₂.

Respiration Equation

Glucose + O₂ → CO₂ + H₂O + ATP.

Photosynthesis Function

Removes CO₂ and produces O₂.

Respiration Function

Breaks glucose to release ATP energy.

Feedback Mechanism

Process that maintains homeostasis (balance).

Negative Feedback Example

Blood sugar regulation with insulin.

Blood Sugar High

Pancreas releases insulin → cells absorb glucose → sugar normalizes.

Body Temperature High

Sweat to cool body.

Body Temperature Low

Shiver to warm body.

Immune System Function

Defends against foreign antigens.

Antigen

Protein marker on cell surface used for identification.

Organ Rejection

Immune system attacks foreign tissue with different antigens.

Immunosuppressant Drugs

Reduce immune response to prevent rejection.

Respiratory Response to Exercise

Breathing rate increases to bring in more O₂.

Circulatory Response to Exercise

Heart rate increases to deliver O₂ and nutrients.

Muscular Response to Exercise

Muscles contract more to move and produce heat.

Sweating Response

Releases heat to cool body.

Enzymes

Proteins that speed up chemical reactions.

Substrate

The molecule an enzyme acts on.

Lock and Key Model (Enzymes)

Enzyme fits only one specific substrate.

Denatured Enzyme

Enzyme changes shape due to wrong pH or temperature and stops working.

ATP Function

Main energy molecule for cells.

ATP Made In

Mitochondria through cellular respiration.

Genetic Variation

Differences in DNA caused by mutations and sexual reproduction.

Natural Selection

Organisms best adapted to environment survive and reproduce.

Evolution Evidence

Fossils, DNA, anatomy, and embryology.

Molecular Evidence

Similar DNA or protein sequences show related species.

Gel Electrophoresis

Lab method to compare DNA patterns between organisms.

Food Chain

Shows direction of energy flow starting with a producer.

Energy Loss in Food Chain

Energy is lost as heat at each trophic level.

Example Food Chain

Cactus → Squirrel → Rattlesnake → Hawk.

Fertilization

Sperm (n) + Egg (n) → Zygote (2n).

Zygote

First cell formed after fertilization.

Where Fertilization Occurs (Humans)

Fallopian tube (oviduct).

Blocked Fallopian Tube

Prevents sperm and egg from meeting → no zygote.