REPRODUCTION Reproduction – The process of producing offspring Two parents – similar looking offspring One parent – identical looking offspring Two Types Asexual Sexual

ASEXUAL REPRODUCTION A single parent passes a complete copy of its genetic information to each of it’s offspring Offspring are identical to parents Four different types of asexual reproduction

Binary Fission Prokaryotes (bacteria) DNA is replicated DNA Attaches to the cell membrane Cell splits – each having the same DNA

FRAGMENTATION Body breaks into several pieces, some or all of the fragments regrow missing parts and develop into adults Ex. Starfish, some worms, some plants

BUDDING New individuals split off from existing ones Ex. Hydra, potatoes, jellyfish, corals

PARTHENOGENESIS Process by which females make a viable egg that grows into an adult without fertilization Ex. Water fleas, some worms, some bees

SEXUAL REPRODUCTION Meiosis Purpose is to produce cells that are genetically different from parents Offspring has traits from each parent, but is different Male – sperm Female - egg

Meiosis Genes are located on chromosomes Each species has a specific number of chromosomes Mosquitoes = 6 Chimpanzees = 48 Humans = 46 Each egg and sperm have 22 autosomes and 1 sex chromosomes and when they come together we have 46

Haploid vs.Diploid Diploid = two sets of chromosomes (46) Haploid = one set of chromosomes (23) Homologous chromosomes = identical to each other Autosomes = chromosomes that do not determine sex Sex chromosomes- determine sex (XX-females, XY-males

Meiosis I Meiosis I – 1st nuclear division Follows a period of interphase - cell growth Divided into 4 phases

Prophase I – chromosomes form from DNA strands, spindle fibers appear, homologous pairs line up and form a tetrad Crossing over may occur – which is when chromosomes exchange portions of their chromatids, resulting in an exchange of genes Heterogenous chromosomes

Metaphase I – tetrads move to the center of the cell

Anaphase I – homologous pairs of chromosomes separate Anaphase I – homologous pairs of chromosomes separate. Each chromosome is still composed of two chromatids joined by a centromere

Telophase I – cytoplasm divides, forming 2 daughter cells

Meiosis II (2nd nuclear division) Occurs in each cell formed during meiosis I, and is not preceded by DNA replication Divided into 4 phases

Prophase II – new spindle fibers form

Metaphase II – chromosomes move to the center of the cell

Anaphase II – the centromeres joining the chromatids divide freeing the sister chromatids from each other, and the chromatids move to opposite poles of the cell

Telophase II – spindle dissolves, nuclear membrane forms, and cytokinesis occurs. Produces four daughter cells

Formation of egg and sperm – forms gametes (sexual reproductive cells) Meiosis in males produces 4 sperm Meiosis in females produces 1 egg and 3 polar bodies which will disintegrate Meiosis allows for genetic recombination. This allows for variation between parent and offspring

GENETIC VARIATION Advantageous for a population in order to survive in their environment Polar bears with a gene for thick fur vs. those with a gene for thin fur. ( Who would survive?) Only made possible by sexual reproduction due to rearranging of genes Read pages, 253 – 254 with a partner together summarize the 3 keys to genetic variation

MULTICELLULAR LIFE CYCLES Life Cycle – all the events in the growth and development of an organism Two types of life cycles Diploid Haploid

DIPLOID LIFE CYCLE Most animals have this Diploid cells go through meiosis and forms gametes (sperm and egg) which join together during fertilization Result is the haploid gamete

HAPLOID LIFE CYCLE Occurs in fungi and some protists A zygote goes through meiosis immediately after it is formed and makes new haploid cells Haploid cells divide by mitosis and create new individuals

Alternation of generations Plants and multicellular organisms that alternate between diploid and haploid Sporophyte; diploid phase of a plant – produces spores through meiosis Gametophyte; haploid phase that produces gamete by mitosis