Science Term 2 Exam- Biology Flashcards
What are the 2 ways to reproduce?
Asexual reproduction
Sexual reproduction
Why do we reproduce?
Reproduction is to produce offspring, pass on your genetics and to ensure your species doesn’t die out
Asexual reproduction
Only requires 1 organism
Often found in some plants and simple animals
Produces clones of the original parent
- they have the same genetic information
Bad characteristics are reproduced
-If the plant cant survive the frost all of the offspring will be vulnerable in the same way because there is no genetic variation
Pro
-Only one organism, doesn’t need to find a mate
What does DNA stand for
Delxyribose Nucleis Acid
What is a amoeba
The cell that divides into 2 identical cells by mitosis
what is a gene?
a gene is a section of DNA that codes for a specific trait/characteristic
what is a chromosome
a threadlike structure of neucleic acids and protein found in the nucleus of the most living cells, carrying genetic information in the form of genes
Everyone has 23 pairs of chromosomes
In one chromosome there is thousands of genes
Sexual Reproduction
You need 2 organisms You get a set of chromosomes from each Produces a genetic variation Pros -Offspring are different, wont be wiped Cons -Needs 2 organisms that are the opposite gender
Sex cells
Sex cells are called gametes
Male- Sperm, pollen
Female- Egg, ovum (ova)
Each contain 23 chromosomes
When a sperm fertilises a egg it is called a zygote
The cell divides after about 3 days it has become 32 cells and it called a embryo
About 9 weeks all its body systems have developed and it called a feutus
What is a Human Karyotype
A visual representation of chromosomes in the cells nucleus
What is Mitosis?
Mitosis creates a new identical cell
What are codes for DNA?
Thymine (T) goes with Adenine (A)
Cytosine (C) goes with Guanine (G)
S goes on the side of these codes
P goss on the outer of S
Chromosomes
23 Pairs a person, we have 46 in total
Each sex cell has 23
Diploid- When there is pairs of chromosomes
What happens if there are too many chromosomes or too few
The person will have mutations eg physical disabilities, strange physical features and more
What is a somatic cell
A normal body cell
If it went under mitosis an exact replica of the cell would be created
Where do different characteristics come from and how do we get them
We get them from our parents. 23 chromosomes from each parent
Eg. A chromosome for eye colour would have the same position but different sequences that code for different eye colours
Alleles is the different form/s of a gene- it can produce different looking traits
The menstruation cycle
Pt 1
What is oestrogen?- During the menstrual cycle, estrogen acts to produce an environment suitable for fertilization, implantation, and nutrition of the early embryo
What is progesterone?- It helps prepare your body for conception and pregnancy and regulates the monthly menstrual cycle.
The menstruation cycle
Pt 2
Day 1 to 4- Lining breaks down, Progesterone levels are down and Oestrogen levels start to rise
Day 4 to 14- Lining builds up, Oestrogen levels are at their highest point + Progesterone levels start to rise
Day 14 to 28- Lining is maintained, Progesterone levels are at its highest point, Oestrogen levels fall
The cycle is then repeated
What happens to the progesterone levels when a egg is fertilised?
The progesterone levels stay high so the egg is not ejected and the lining degrades
The first trimester
Weeks 1-13
Big hormone change
Uterus begins to support growth of placenta
Body adds to its blood supply for nutrition and oxygen to baby
Morning sickness, headaches, constipation
Baby is very vulnerable to alcohol, drugs and smoking- Fetal Alcohol Syndrome
The second trimester
Week 13-27 Many early signs of pregnancy disappear Abdomen starts to look pregnant Stretch Marks and backaches Baby is 4x as big at the end then it was Week 24 onwards the baby has lungs so it can survive if born
The third trimester
28th week until birth Baby continues to get bigger All organs have formed Baby puts pressure on mothers organs Baby moves head down, preparing for birth
Labor- First stage
Contractions start
Cervix thins out and dilates (starts to open)
Last 12-19 Hours
It ends when it is fully open
Labour second stage-
Giving birth to the baby
Lasts 20 mins to 2h
Labour third stage-
Delivery of the placenta
5-30 mins
What is a pedigree chart?
A family tree/chart
Symbols for pedigree charts
A single line that connects two people- married
A line that descends into a horizontal line and connects to other people through vertical lines- Offspring (Left is the oldest and right is the youngest)
Doing the same thing but with both lines attaching straight onto the marriage line with no line between the offspring means non identical twins, if there is a line between them it means identical twins
Mutations
Mutations are changes to your DNA caused by da,age by the environment or copying errors in the chromosomes
Punnet squares
The genotype is written like BB, Bb, bb and shows the allele combination
The genotype determines the physical traits called a Phenotype
What is homozygous and heterozygous?
Homozygous is when we have a combination with either two big letters or two small letters in the alleles
Heterozygous is when there are both a big letter and small letter in the alleles
What is an alleles
The different forms of a gene that can produce different physical traits for specific physical traits
What is the difference between chromosomes genes and DNA
Dna is a double helix made of bases sugars and phosphates
Chromosomes are apart of dna that contains genes
Genes are a specific part of a chromosome that code for a trait/characteristic
