Biology Paper Two Flashcards
What is Homeostasis?
Homeostasis is the maintenance of a constant internal environment.
What happens if a stimulus is too high?
- Receptors detect a stimulus is too high.
- The coordination centre receives and processes the information, then organises a response.
- Effector produces a response which counteracts the change and restores the optimum level.
- The effectors will continue to produce the response for as long as they’re needed.
What is the nervous system?
- CNS (Central Nervous System)
- Sensory neurones
- Motor neurones
- Effectors
What are sensory neurones?
The neurones that carry information as electrical impulses from the receptors.
What are motor neurones?
The neurones that carry electrical impulses from the CNS to effectors.
What are effectors?
Muscles and glands which respond to nervous impulses.
What are synapses?
Connection between two neurones. The nerve signal is transferred by chemicals which diffuse across the gap.
What are the 4 parts of the brain?
Cerebral Cortex: outer wrinkly bit, it’s responsible for things like consciousness, intelligence, memory and language.
Medulla: Controls unconscious activities e.g breathing and heartbeat.
Cerebellum: Responsible for muscle coordination.
Spinal Cord
What are ways that scientists study the brain?
- Studying patients with brain damage
- Electrically stimulating the brain
- MRI Scans
What is the Sclera, Cornea and Iris?
Sclera: the tough, supporting wall of the eye.
Cornea: the transparent outer layer at the front of the eye, it refracts light into the eye.
Iris: contains muscle that allow it to control the diameter of the pupil, therefore how much light enters the eye.
What is the Lens, Retina, Ciliary Muscles and Suspensory Ligaments?
Lens: focuses the light onto the retina
Retina: contains rods and cones
Ciliary and Suspensory Ligaments control the shape of the lens.
What are the 4 stages of the menstrual cycle?
Stage 1: Day 1 - Menstruation starts, the uterus lining breaks down.
Stage 2: The uterus builds up again, from day 4 - 14.
Stage 3: An egg develops and is released from the ovary at day 14, this is called ovulation.
Stage 4: The wall is maintained and cycle restarts if no egg is fertilised.
What is FSH?
Follicle-Stimulating Hormone
- Produced in the pituitary gland.
- Causes an egg to mature in one of the ovaries, in a structure called a follicide.
- Stimulates the ovaries to produce oestrogen.
What is oestrogen?
- Produced in the ovaries.
- Causes the lining of the uterus to grow.
- Stimulates the release of LH and inhibits the release of FSH.
What is LH?
Luteinising Hormone
- Produced by the pituitary gland.
- Stimulates the release of an egg.
What is progesterone?
- Produced in the ovaries by the remains of the follicle.
- Maintains the lining of the uterus in the second half of the cycle.
- Inhibits the release of LH and FSH
What is the plant hormone that controls growth?
Auxin.
What is DNA?
Deoxyribonucleic acid.
- Contains coded information
- Found in the nucleus, in chromosomes
What is a gene?
A gene is a small section of DNA found on a chromosome.
Each gene codes for a particular sequence of amino acids, which are put together to make a specific protein.
What is a genome?
The entire set of genetic material in an organism.
What is mRNA?
Proteins are made in ribosomes. They use a molecule called mRNA from DNA to code for these proteins.
What are the different functions of proteins?
Enzymes
Hormones
Structural Proteins
What is meiosis?
Produces cells which have half the normal number of chromosomes. 4 gametes are produced.
What is cystic fibrosis?
A genetic disorder. It produces sticky mucus in air passages.
- It’s a recessive allele carried by 1 in 25.
What is polydactyly?
A genetic disorder where a baby is born with extra fingers of toes.
- Dominant allele.
What are the pros and cons of Embryonic Screening?
+ It will stop people suffering.
+ Costs the government.
+ There are laws to stop it going too far.
- Could increase prejudice.
- May come a point where everyone wants to screen their baby.
- Expensive.
What is selective breeding?
When humans artificially select the plants or animals that are going to breed so that the genes for particular characteristics remain in the population.
How can plants be cloned?
Tissue Culture:
- A few plant cells are put in a growth medium with hormones. They grow into clones of the parent plant.
- These plants can be made very quickly.
- Tissue culture is used by scientists to preserve rare plants that are hard to reproduce.
Cuttings:
- Take cuttings of good plants and then plant them to produce identical ones.
- Quick and cheap.
- Older and simpler method.
What is adult cell cloning?
- Adult cell cloning involves taking an unfertilised egg cell and removing its nucleus.
- The nucleus is then removed from an adult body cell and inserted into the empty egg cell.
- The egg is then stimulated by an electric shock, this makes it divide.
- When the embryo is a ball of cells, it’s implanted into the womb of an adult female.
How are fossils formed?
From gradual replacement by minerals:
1. Things that don’t decay easily (e.g bones) last a long time while buried.
2. They are eventually replaced by minerals as they decay. Which forms a rock-like substance.
3. The surrounding sediments also turn to rock but the fossil stays distinct.
Form casts and impressions:
1. When an organism is buried in a soft material. This then hardens around it. This leaves a cast around itself.
From preservation in places where no decay happens:
1. In amber and tar pits there is no oxygen or moisture so decay microbes can’t survive.
2. In glaciers it’s too cold for the decay microbes to work.
3. Peat bogs are too acidic for decay microbes.
What is speciation?
The development of a new species.
This occurs when populations of the same species become so different that they can no longer successfully interbreed to produce fertile offspring.
What is natural selection?
- Isolation is where populations of a species are separated.
- Isolation can happen due to a physical barrier e.g floods and earthquakes.
- Conditions on either side of the barrier will be slightly different e.g different climates.
- Because the environment is different on each side, different characteristics will become more common in each population.
- Eventually the individuals from the different populations will have changed so much that they won’t be able to breed.
How can bacteria evolve and become antibiotic-resistant?
- Some bacteria can develop random mutations in their DNA. This can lead to them becoming resistant to a particular antibiotic. This leads to antibiotic-resistant strains.
- These then reproduce rapidly.
- This increases the amount of resistant bacteria.
- This is easily spread.
- MRSA is a common superbug.
What is classification?
Organising living organisms into groups.
What are the different classifications? (7)
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
Define a Herbivore.
Primary consumers that eat plants/algae.
What is a Tertiary consumer?
Carnivores that eat other carnivores.
What is an apex predator?
Predatorial carnivores that themselves do not have any predators.
What does a decomposer do?
Secretes enzymes into the environment by breaking down dead matter.
What is coral bleaching and when does it occur?
When coral polyps expel algae that lives inside their tissues.
What causes coral bleaching?
Warmer water temperature.
What relationship is crucial in order to maintain the health of a reef?
Symbiotic relationship between coral and algae.
What causes water temp to rise? (5)
Global warming. Run off (dilution). Pollution. Over exposure to sunlight. Extreme low tides.
Name an alternative to monoculture.
Crop rotation.
What is crop rotation?
Different crops being planted each year in the same field.