Science biology

• Mitosis- is the process by which a single cell divides into two identical daughter cells. This type of division is essential for growth and repair in multicellular organisms, as well as for asexual reproduction in some single- celled organisms.
• Meiosis- is the process by which a single cell divides into four daughter cells, each with half the number of chromosomes of the parent cell. And is critical for sexual reproduction, as it allows for the.. production.of gametes.
• During prophase- the chromatin in the nucleus condenses into visible chromosomes, which become visible under a microscope. The centrosomes, which are responsible for organizing the spindle fibers, move to opposite poles of the cell. The nuclear envelope breaks down, allowing the spindle fibers to attach to the chromosomes.
• During metaphase- , the chromosomes line up along the equator of the cell, called the metaphase plate. The spindle fibers, which are attached to the centromeres of each chromosome, ensure that the chromosomes are properly aligned and can be separated correctly.
• Anaphase - During this stage, the sister chromatids of each replicated chromosome separate and are pulled towards opposite poles of the cell by the spindle fibers.

  This results in the formation of two identical sets of chromosomes at opposite poles of the cell.
• During telophase-, the chromosomes reach the opposite poles of the cell, and the nuclear envelope begins to reform around each set of chromosomes. The chromosomes begin to uncoil and return to their normal, diffuse form. The spindle fibers disassemble, and the cell begins to prepare for cytokinesis.
• Cytokinesis- is the process by which the cell divides into two daughter cells.

  In animal cells, a contractile ring of actin and myosin filaments forms around the cell, contracting and pinching the cell membrane until the cell is divided into two separate cells.

  In plant cells, a structure called the cell plate forms along the equator of the cell, eventually dividing the cell into two separate daughter cells.
• What is meiosis? A type of cell division where a single cell divides twice and produces four daughter cells with half the amount of genetic material (sex cells).
• PROPHASE 1- The chromosomes condense and the nucleolus breaks down. As chromosomes move around, crossing over happens - this means genetic material can be exchanged.
• METAPHASE 1- The chromosomes align in pairs in the centre of the cell. Random assortment occurs - this means that chromosome pairs line up randomly.
• ANAPHASE 1- Chromosome pairs separate and move to opposite ends of the cell. This ensures each cell contains half the number of chromosomes (haploid).
• TELOPHASE 1 -

  Two new nuclei form around each set of chromosomes.

  The cytoplasm splits and two (haploid) daughter cells are formed.
• PROPHASE 2- Phase 2 happens to allow 4 haploid sex cells (sperm and egg cells) to be created. The chromosomes condense and the nucleolus breaks in both cells.
• METAPHASE 2 -

  The chromosomes align single file in the centre of the cell.

  This occurs to ensure sister chromatids separate in the next stage.
• ANAPHASE 2- Sister chromatids separate and move to opposite ends of the cell. This ensures the daughter cells remain haploid - that means they have half the genetic material of the original parent cell.
• TELOPHASE 2 -

  Four new nuclei form around each set of chromosomes

  The cytoplasms split and four (haploid) daughter cells are formed.
• Genetic diversity -pertains to the difference in the genetic composition of each organism e.g. Beagle, Shih
• Ecosystem diversity -concerns the different kinds of places where organisms live and the interconnections that bind these organisms together
• Species diversity- deals with the different kinds of organisms
• Biodiversity- is coined from the words "biological diversity". It describes how varied living things are in a certain area - plants, animals, fungi, and microorganisms as well as the community they form and the habitat they are living in.
• Species diversity -pertains to the number of species and abundance of every species in a given community.
• Species diversity- talks about the difference within species or difference between similar species. A species is the fundamental unit of diversity. It is an individual not a class, nor genera. It will take long enough to develop another trait if a group of individuals remains isolated from the rest of its species.
• High diversity -places consist of numerous kinds of species.
• Low diversity -places may be highly populated but may not be diverse.
• 1. Typological Species Concept- defines species as a group whose members share certain characteristics that distinguish them from other species;
• 2. Biological Species Concept- considers species as a distinguished group of populations whose members are capable of interbreeding successfully and are reproductively isolated from the other groups to produce fertile offspring.
• 3. Phylogenetic Species Concept - defines species as a group of organisms with a shared, unique genetic history. It uses this concept to classify species by looking at a group whose members come from a common ancestor and have shared a unique evolutionary history, possessing a combination of certain defining, or derived traits.
• Species richness- is the simplest measurement of species diversity. It relates to the number of species inhabiting a given area or habitat as shown in figure 5.
• Species evenness- measures how many individual organisms belong to each species. It refers to the similarity in numbers or equal abundance of species in a particular area. Figure 6 shows 5 individuals for each species.
• Species dominance- refers to a dominant species distributed across a given area. Figure 7 shows that one species has the Most number of individuals compared to other species.