Biology: Cell Division, Meiosis, Cell Transport

What is mitosis?→A type of cell division that produces genetically identical cells.

What is a nucleus?→A sub-cellular structure that contains the genetic material (DNA); controls the cell activities.

What is a chromosome→ Tightly coiled strands of DNA that carry the genetic material.

Why is cell division important?

• For growth e.g. the growth of plant seed

• For repair of damaged tissue e.g. broken arm on an x-ray

• For asexual reproduction

What are the name of each stages for the cell cycle?

• Stage 1: Cell growth

• Stage 2: mitosis - nuclear division

• Stage 3: division of the cell membrane & cytoplasm

What happens in the first stage of cell cycle?

• Each chromosome is copied

• ribosomes & mitochondria are copied

• the cell grows larger

• the cell has twice the amount of DNA

• this ensures the daughter cells have the full set of chromosomes once the cell has divided.

What happens in the second stage of the cell cycle?

• the chromosomes line up at the equator of the cell and the cell fibres pull each chromosomes of the 'X' to either side of the cell.

• the nucleus divides

What happens in the third stage of the cell cycle?

• Two identical daughter cells form when the cytoplasm and cell membranes divide.

What is sexual reproduction?→type of reproduction that combines the genetic material of two organisms to produce genetically different offspring

What are gametes?→An organism's sex cells that contain half the number of chromosomes.

What is meiosis?→a type of cell division that forms the gametes.

What is a haploid?→a cell with half the number of chromosomes

Describe the difference between asexual & sexual reproduction?

• Asexual reproduction requires only one organism and the resulting offspring are genetically identical to the parent cell (clones).

• Sexual reproduction requires two organisms and involves gametes fusing together to form genetically different offspring.

• How many chromosomes does a sperm have?→23 chromosomes

• Is sperm an haploid or a diploid?→haploid

• Is sperm a gamete?→yes

• How many chromosomes does a egg have?→23 chromosomes

• Is egg an haploid or a diploid?→haploid

• Is egg a gamete?→yes

• is an egg found in males, females or both?→female

• How many chromosomes does a zygote?→46 chromosomes, 23 pairs

• Is a zygote a haploid or diploid?→diploid

• Is a zygote a gamete?→no

• Are zygotes found in males, females or both?→both

• Explain why it is important for gametes to be haploid?

  • During fertilisation the sperm and egg cell fuse together to form a zygote

  • The zygote has to have the full number of chromosomes (46 or 23 pairs)

  • Therefore, each gamete must have half the number of chromosomes to ensure the zygote is diploid.

• What happens before the process of meiosis can occur (first stage of meiosis)→the DNA is copied during interphase.

• What happens at the second stage of meiosis?

  • after chromosomes are replicated, they arrange themselves into pairs and line up along the middle of the cell.

  • DNA mixing between maternal & paternal DNA occurs; this creates variation within the chromosomes.

What happens at the third stage of meiosis?

• The chromosomes get pulled to either end of the cell and the first cell division occurs.

• Two diploid cells are created.

• (some chromosomes contain a mixture of DNA leading to genetic variation)

What happens at the fourth stage of meiosis?

• Chromosomes line up along the middle of the cell and are pulled to either end.

• Second cell division occurs, creating four haploid gametes.

What are the uses of mitosis?

• Asexual reproduction in some unicellular organisms e.g. yeast

• Growth and repair in multicellular organisms

What are the uses of meiosis?

• used to form gametes (sex cells)

What are the differences between the number of cell divisions and cells produced in mitosis & meiosis?

• Mitosis only involves one cell division & produces two cells.

• Meiosis involves two cell divisions and results in 4 cells.

What are the differences between the amount of genetic material in cells produced in mitosis & meiosis?

• Mitosis produced diploid cells with two copies of each chromosome; a full set of chromosomes.

• Meiosis produces haploid cells with one copy of each chromosome; half a set of chromosomes.

What are the differences between the genetic variation in cells produced in mitosis & meiosis?:

• Mitosis usually produces genetically identical cells.

• In meiosis the parental DNA mixes which causes genetic variation in the gametes produced.

What are the differences in the roles that mitosis & meiosis play in sexual reproduction in humans?

• In Meiosis, gametes are made through the process of meiosis

• In Mitosis, after fertilisation the zygote is formed

• the zygote cell divides by mitosis to produce two genetically identical cells.

• these cells keep dividing by mitosis to form an embryo.

What is diffusion - random movement of a substance (solutions & gases), high to low concentration

What is osmosis - movement of water, high concentration to low concentration

What is the concentration gradient - difference in concentration between a region of high con to lower con

What is active transport - substances have to be moved from a low to a high concentration - against a concentration gradient, requires cell energy atp

the bigger the concentration gradient the faster the diffusion rate

higher temp = faster diffusion rate

rate of of transport is dependant on the size, temperature, concentration gradient of the substance

Biodiversity is the range of different living organisms that live in a place. The higher the number of different organisms that live in an ecosystem, the greater its biodiversity.

• Biodiversity is an key indicator of the health of an ecosystem (e.g. climate change)

• Arctic habitats do not have a high biodiversity.

• It is a harsh environment, and few species can live there.

• Coral reefs have a high biodiversity.

• Coral reefs contain lots of food, shelter and places for many different species to reproduce.

Why is having a high biodiversity imporatant for humans - humans rely on many different organisms for food, medicines and resources (e.g. materials)

as the human population increases = our activities have a negative impact on biodiversity

These include:

• increased land use for resources (e.g. food and fuels)

• increased urbanisation

• • increased production of waste and pollution

why is biodiversity decreasing as the human population increases?

ecosystems are being destroyed as humans use more land to grow single crops for food.

ecosystems are put under pressure as a result of pollution and waste produced by humans

Biodiversity - all the different kinds of life you find one area - varity of animals, plants, fungi, microorganisms, like bacteria that make up our nature world, they work together in one ecosystem