--- title: "Egg Cell | General Biology I" description: "Egg cell in General Biology I: the female gamete that carries half the DNA, supports fertilization, and supplies early nutrients after ovulation." canonical: "https://fiveable.me/college-bio/key-terms/egg-cell" type: "key-term" subject: "General Biology I" unit: "Unit 32" --- # Egg Cell | General Biology I ## Definition An egg cell, or ovum, is the female gamete in General Biology I. It carries half the chromosomes needed for fertilization and provides nutrients for the early embryo. ## What It Is In General Biology I, the egg cell is the female gamete, the reproductive cell that can fuse with a sperm cell during sexual reproduction. It is usually large, nutrient-rich, and haploid, meaning it carries one set of chromosomes instead of two. An egg cell is made in the ovaries through oogenesis. That process does not usually make many usable eggs at once. Instead, one cell develops into a mature egg, while the others from that cycle often do not continue. In humans and many animals, ovulation releases a mature egg cell from the ovary so it can travel into the reproductive tract. What makes the egg cell different from sperm is not just size. The egg contributes most of the cytoplasm, organelles, and stored materials that the first stages of development need. That is why the egg is often described as the “resource” cell, while the sperm is the delivery cell for the male genetic contribution. The egg cell does not develop into an embryo by itself. Fertilization has to happen first, which means a sperm cell fuses with the egg cell and the two haploid nuclei combine to form a diploid zygote. Once that happens, the new cell can begin early embryonic divisions. Timing matters a lot. In many species, the egg remains viable for only a short window after ovulation. If fertilization does not happen in that window, the egg breaks down and is absorbed or passed out of the reproductive tract. That short lifespan is one reason reproductive cycles are tightly regulated by hormones. In a college biology lab or lecture, you will usually meet the egg cell as part of bigger topics like gamete formation, fertilization, and early development. It is the starting point for tracing how sexual reproduction produces a genetically unique offspring. ## Why It Matters The egg cell is one of the clearest examples of how form matches function in biology. Its large size, haploid chromosome set, and nutrient stores all connect directly to what happens after fertilization. If you understand the egg cell, a lot of reproductive biology becomes easier to trace, from ovulation to zygote formation. It also gives you a clean way to compare male and female gametes. Sperm and egg are both haploid, but they are built for different jobs. The egg contributes the cellular machinery and early food supply, while sperm is streamlined for movement and DNA delivery. In General Biology I, the egg cell shows up whenever you study sexual reproduction, meiosis, and embryonic development. It also helps explain why fertilization is a narrow event rather than something that can happen anytime. The egg’s short viability window, along with the timing of sperm arrival, shapes the whole reproductive process. You will also see the egg cell again in plant reproduction, where the female gamete is inside the embryo sac. That makes the term useful beyond animals, since the basic idea stays the same: a haploid female cell that joins with a male gamete to begin a new organism. ## Connections ### [Sperm Cell](/college-bio/key-terms/sperm-cell) The sperm cell is the egg cell’s partner in fertilization. Both are haploid gametes, but sperm is small, motile, and specialized to reach the egg, while the egg is large and packed with cytoplasm and nutrients. Comparing them helps you see how sexual reproduction splits reproductive labor between two very different cells. ### Fertilization Fertilization is the step that turns an egg cell into the start of a new diploid organism. The egg does not become an embryo until a sperm cell fuses with it and their genetic material combines. If you are tracing the reproductive process, the egg is the starting cell and fertilization is the event that changes its status. ### Zygote A zygote forms right after the egg cell and sperm cell fuse. The egg gives up one haploid set of chromosomes, and the sperm gives the other, creating the first diploid cell of the next generation. In problems about early development, the egg cell is the precursor and the zygote is the first product. ### [Embryo Sac](/college-bio/key-terms/embryo-sac) In flowering plants, the egg cell is found inside the embryo sac rather than in an ovary like in animals. The embryo sac is the female structure where the egg waits to be fertilized by pollen-derived sperm cells. This connection matters when you switch from animal reproduction to plant reproduction in General Biology I. ## On the AP Exam A quiz or lab question may ask you to identify the egg cell in a diagram, compare it with sperm, or trace what happens before and after fertilization. You might also need to explain why the egg is haploid, why it carries more cytoplasm than sperm, or how ovulation fits into the reproductive cycle. In plant biology questions, the term can show up inside the embryo sac and be connected to pollen tube delivery. For short-answer prompts, the best move is to link structure to function: large size, nutrient supply, and readiness for fusion. ## egg cell vs zygote The egg cell is the unfertilized female gamete, while the zygote is the new diploid cell formed after fertilization. A quick way to separate them is to ask whether sperm has already fused with the cell. If yes, you are looking at a zygote, not an egg cell. ## Key Takeaways - The egg cell is the female gamete in sexual reproduction, and it is haploid. - Its large cytoplasm and nutrient stores support the earliest stages after fertilization. - Ovulation releases a mature egg, but it can only be fertilized for a limited time. - Fertilization happens when sperm and egg fuse to form a zygote. - In plants, the same basic idea appears in the embryo sac rather than an animal ovary. ## FAQs ### What is egg cell in General Biology I? The egg cell is the female reproductive cell, or gamete, in sexually reproducing organisms. It carries one set of chromosomes and can fuse with a sperm cell to form a zygote. In biology, it is also called the ovum in many animal contexts. ### How is an egg cell different from a sperm cell? Both cells are haploid, but they are built for different jobs. The egg cell is larger and holds more cytoplasm and nutrients, while the sperm cell is smaller and usually motile. That difference matches their roles in fertilization. ### What happens to an egg cell after ovulation? After ovulation, the egg cell moves into the reproductive tract and waits for fertilization. If a sperm cell reaches it in time, the two fuse and form a zygote. If not, the egg breaks down and is no longer viable. ### Where is the egg cell found in plants? In flowering plants, the egg cell is inside the embryo sac of the ovule. Pollen delivers sperm cells to that location so fertilization can occur. This is the plant version of the same basic gamete-fusion process you see in animals. ## Related Study Guides - [32.2 Pollination and Fertilization](/college-bio/unit-32/2-pollination-fertilization/study-guide/l494ZOin1pZHS3Wy) ## About This Document Canonical Fiveable pages are available as Markdown at the same path plus `.md`. - [llms.txt](https://fiveable.me/llms.txt): index of Fiveable's sections and URL patterns - [llms-full.txt](https://fiveable.me/llms-full.txt): complete subject and unit listing - [MCP server](https://fiveable.me/mcp): call Fiveable as tools instead of fetching pages (`https://fiveable.me/api/mcp`) - [MCP server for AP teachers](https://fiveable.me/mcp/teachers): a teacher's classes, assignments and AP-rubric grading (`https://fiveable.me/api/mcp/teacher`) ## Structured Data ```json {"@context":"https://schema.org","@graph":[{"@type":"LearningResource","@id":"https://fiveable.me/college-bio/key-terms/egg-cell#resource","name":"Egg Cell | General Biology I","url":"https://fiveable.me/college-bio/key-terms/egg-cell","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/college-bio/key-terms/egg-cell#term"},"audience":{"@type":"EducationalAudience","educationalRole":"student"},"dateModified":"2026-07-03T02:21:09.278Z","isPartOf":{"@type":"Collection","name":"General Biology I Key Terms","url":"https://fiveable.me/college-bio/key-terms"},"publisher":{"@type":"Organization","name":"Fiveable","url":"https://fiveable.me"}},{"@type":"DefinedTerm","@id":"https://fiveable.me/college-bio/key-terms/egg-cell#term","name":"egg cell","description":"An egg cell, or ovum, is the female gamete in General Biology I. It carries half the chromosomes needed for fertilization and provides nutrients for the early embryo.","url":"https://fiveable.me/college-bio/key-terms/egg-cell","inDefinedTermSet":{"@type":"DefinedTermSet","name":"General Biology I Key Terms","url":"https://fiveable.me/college-bio/key-terms"}},{"@type":"FAQPage","mainEntity":[{"@type":"Question","name":"What is egg cell in General Biology I?","acceptedAnswer":{"@type":"Answer","text":"The egg cell is the female reproductive cell, or gamete, in sexually reproducing organisms. It carries one set of chromosomes and can fuse with a sperm cell to form a zygote. In biology, it is also called the ovum in many animal contexts."}},{"@type":"Question","name":"How is an egg cell different from a sperm cell?","acceptedAnswer":{"@type":"Answer","text":"Both cells are haploid, but they are built for different jobs. The egg cell is larger and holds more cytoplasm and nutrients, while the sperm cell is smaller and usually motile. That difference matches their roles in fertilization."}},{"@type":"Question","name":"What happens to an egg cell after ovulation?","acceptedAnswer":{"@type":"Answer","text":"After ovulation, the egg cell moves into the reproductive tract and waits for fertilization. If a sperm cell reaches it in time, the two fuse and form a zygote. If not, the egg breaks down and is no longer viable."}},{"@type":"Question","name":"Where is the egg cell found in plants?","acceptedAnswer":{"@type":"Answer","text":"In flowering plants, the egg cell is inside the embryo sac of the ovule. Pollen delivers sperm cells to that location so fertilization can occur. This is the plant version of the same basic gamete-fusion process you see in animals."}}]},{"@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"General Biology I","item":"https://fiveable.me/college-bio"},{"@type":"ListItem","position":2,"name":"Key Terms","item":"https://fiveable.me/college-bio/key-terms"},{"@type":"ListItem","position":3,"name":"Unit 32","item":"https://fiveable.me/college-bio/unit-32"},{"@type":"ListItem","position":4,"name":"egg cell"}]}]} ```