Transcript Lecture 31
I. Female Reproductive System A. Ovaries 1. contain oocytes - humans: about 2 million at birth a. primary oocytes I. Female Reproductive System A. Ovaries 1. contain oocytes - humans: about 2 million at birth a. primary oocytes b. arrested in prophase I of meiosis 2. ovulation a. hormonal fluctuations b. 400-480/lifetime (human) c. ovum d. is a phase of the estrous cycle B. Oviducts 1. tubes lined with smooth muscle 2. peristalsis - journey takes 5-7 days in humans 3. fertilization occurs here - in the first 1/3 - 24 hour window of egg viability (human) C. Uterus 1. endometrium: inner lining where embryo implants 2. muscular walls (myometrium) 3. cervix 4. horns - diverse horn structures among mammals II. Embryonic Development (human) A. Cleavage (is a type of reduction division) 1. first division about 30 hours after fertilization 2. morula = solid ball of cells - typically the 32-cell stage 3. blastocyst (blastula in some other organisms) a. hollow ball of cells (contains a blastocoel) b. implantation (around 128-cell stage) c. trophoblast (outer layer of cells) - gives rise to fetal placenta and other membranes B. Extraembryonic membranes 1. form after implantation 2. trophoblast contributes to these membranes 3. amnion - encloses the fluid-filled amniotic sac containing embryo 4. chorion - becomes the fetal portion of the placenta C. Gastrulation - embryonic cells sorted into distinct layers: 1. endoderm (becomes lining of the gut tube) 2. mesoderm (becomes “internal structures”) 3. ectoderm (becomes nerves and skin) 5 weeks 9 weeks 14 weeks I. Ecology (Chapter 34.1) A. How organisms react to their environment B. Varies by location 1. community - all of the populations of different species living in a particular place - the biotic components of an ecosystem 2. physical habitat - the physical place where a community lives - the abiotic components of an ecosystem - rocks, water, ground, wind, sun 3. ecosystem = community + habitat II. Energy Flow (Chapter 37.8-9; 37.14-17) A. Starts with the sun 1. photosynthesis 2. light energy to chemical energy 3. energy stored in organic molecules (like glucose) B. Producers 1. carry out photosynthesis - plants, algae, cyanobacteria 2. lowest trophic level - is the number of consumption levels away from the sun 3. produce “usable” energy sources - in the process they use CO2 and nitrogen C. Consumers 1. herbivores - level 2 - are the primary consumers - most can digest cellulose 2. carnivores - level 3 - secondary consumers - sometimes level 4 or 5 (tertiary or quaternary consumers) 3. omnivores - get starches and some simple sugars from plants - typically cannot digest cellulose 4. detritovores/decomposers - get their nutrients/energy from detritus - mainly bacteria and fungi - but includes many animals (scavengers) Complex food webs D. Limitations of food chains (food webs) 1. much energy used by producers lost as heat (often 50%) - also can’t get energy from everything ingested (lost as waste) 2. herbivore utilizes only 10% of energy stored in plant molecules 3. carnivore utilizes only 10% of energy stored in herbivore 4. rarely over 4 or 5 trophic levels in an ecosystem What is the best way to utilize 10 pounds of grain?